· web viewthe word ‘diameter’ or ‘radius’ was hardly ever seen. (d) only a very small...
TRANSCRIPT
P3 09 Circular Motion
140 minutes
140 marks
Q1. The diagram below shows the orbits for two types of satellite, a polar orbit and a geostationary orbit.
A satellite in stable Earth orbit moves at a constant speed in a circular orbit because there is a single force acting on it.
(i) What is the direction of this force?
.....................................................................................................................................(1)
(ii) What is the cause of this force?
.....................................................................................................................................(1)
(iii) What is the effect of this force on the velocity of the satellite?
.....................................................................................................................................(1)
(iv) In which of the orbits shown above would this force be bigger?Explain the reason for your answer.
.....................................................................................................................................
.....................................................................................................................................
(2)
(v) Explain why the kinetic energy of the satellite remains constant.
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................(2)
(Total 7 marks)
Q2. (a) A student has fastened a ball to a piece of string and is swinging it round in a horizontal circle.
(i) The diagram below shows an overhead view of the movement of the ball.
Add an arrow, from the centre of the ball, to show the direction in which the ball would move if the string broke at this instant.
(1)
(ii) Complete the table to show how force F changes if the student changes what he is doing. In each case, all the other factors stay the same.
If the student Force F needs to
uses a ball with a greater mass
.................................................
swings the ball at a greater
speed .................................................
swings the ball with a shorter
piece of string .................................................
(3)
(b) The Moon orbits the Earth in a circular path. Use words from the box to complete thethree spaces in the sentence.
direction resistance speed velocity
You may use each word once, more than once or not at all.
The Moon’s ................................. is constant but its .......................................... changes
because its .......................................... changes.(2)
(c) When any object moves in a circular, or nearly circular, path a force must act towards the centre of the circle.
(i) What word is used to describe this force?
...........................................................................................................................(1)
(ii) The Moon orbits the Earth. What provides the force towards the Earth?
...........................................................................................................................(1)
(iii) In an atom, name the particles which are moving in circular paths around the nucleus.
...........................................................................................................................(1)
(iv) In the case of an atom, what word describes the forces which keep these particles moving in circular paths around the nucleus?
...........................................................................................................................
(1)(Total 10 marks)
Q3. Malik uses a camera to photograph the Moon.
(a) Complete each sentence by choosing the correct words from the box.
You may use each word once, more than once or not at all.
converging diverging image longer
object real shorter virtual
In a camera a ........................................ lens is used to produce an ............................
of an ........................................ on a film. The ........................................ is smaller than
the ........................................ and it is a ........................................ distance from the lens.(6)
(b) The Moon moves in a nearly circular path around the Earth.
(i) What is the name of the force which causes the Moon to move around the Earth?
...........................................................................................................................(1)
(ii) In which direction does this force act?
...........................................................................................................................(1)
(c) A force is needed to make a car change direction when it goes round a bend.
(i) What is the name of this force and where does it act?
...........................................................................................................................
...........................................................................................................................(2)
(ii) Complete the two spaces in the sentence.
The force needed is greater if the ........................................ of the car is greater and
the ........................................ of the bend is smaller.(2)
(d) What word is used to describe any force which causes an object to move in a circular path?
....................................................................................................................................(1)
(Total 13 marks)
Q4. The London Eye is the largest observation wheel in the world.
The passengers ride in capsules. Each capsule moves in a circular path and accelerates.
(a) Explain how the wheel can move at a steady speed and the capsules accelerate at thesame time.
....................................................................................................................................
....................................................................................................................................
....................................................................................................................................(2)
(b) In which direction does each capsule accelerate?
....................................................................................................................................(1)
(c) What is the name of the resultant force that causes the capsules to accelerate?
....................................................................................................................................(1)
(d) The designers of the London Eye had to consider three factors which affect the resultant force described in part (c).
Two factors that increase the resultant force are
• an increase in the speed of rotation• an increase in the total mass of the wheel, the capsules and the passengers.
Name the other factor that affects the resultant force and state what effect it has on the resultant force.
....................................................................................................................................
....................................................................................................................................(1)
(Total 5 marks)
Q5. A girl and her father visit a children’s playground.
(a) The diagram shows the girl holding on to a roundabout which is turning.
A centripetal force must act because the girl moves in a circular path.
(i) In which direction, P, Q, R or S, does the centripetal force act?
Direction ..........(1)
(ii) What provides this centripetal force?
..........................................................................................................................
..........................................................................................................................(1)
(iii) Her father pushes the roundabout so that it turns faster. The girl continues to stand on the same part of the roundabout.
Complete the following sentence by drawing a ring around the correct line in the box.
The centripetal force on the girl
decreases
does not change
increases
(1)
(b) The diagram shows the girl and her father on a see-saw.
(i) Use the equation in the box to calculate the moment of the girl.
moment = force × perpendicular distance from the line of action of the force to the axis of rotation
..........................................................................................................................
..........................................................................................................................
Moment of the girl = ....................................... Nm(2)
(ii) What must her father do to increase his moment?
..........................................................................................................................
..........................................................................................................................(1)
(c) The diagram shows part of a level road that they take when they drive home. They drive at a steady speed.
(i) At which point, A, B, C or D, will the centripetal force on the car be greatest?
Centripetal force is greatest at .................... .(1)
(ii) What provides the centripetal force when the car goes round a bend?
..........................................................................................................................
..........................................................................................................................(1)
(Total 8 marks)
Q6. The diagram shows two children playing with a toy called a swing ball. The ball is joined to a pole by a strong string. The children hit the ball so that it goes round in a circular path.
(a) Which force causes the ball to move in a circle?
Draw a ring around your answer.
air resistance tension weight(1)
(b) Complete the sentences by ticking ( ) the correct ending.
(i) The force needed to make the ball move in a circular path is larger if
the speed of the ball is increased.
the speed of the ball is decreased.
the string is made longer. (1)
(ii) The continuous acceleration of a ball moving in a circular path changes
the speed of the ball.
the direction of the ball.
the weight of the ball. (1)
(c) Which of the following words is used to describe any force that causes an object to move in a circular path?
Draw a ring around your answer.
centripetal frictional gravitational universal(1)
(Total 4 marks)
Q7. The drawing shows a set of carriages on a roller coaster.The carriages are moving upwards in a nearly circular path at a constant speed.
(a) Complete the following sentences by drawing a ring around the correct line in each box.
(i) The carriages will accelerate because of a change in their
direction
mass
speed
.
(1)
(ii) The resultant force which causes the carriages to accelerate is the
circular
centripetal
gravity force.
(1)
(b) In which direction, A, B, C or D, does the resultant force act?
Write your answer in the box. (1)
(c) Complete the following sentence by drawing a ring around the correct line in the box.
The resultant force will need to be greater if the
mass of the passengers is greater
radius of the circle is greater
speed of the carriages is less
.
(1)(Total 4 marks)
Q8. This page is from a science magazine.
The Red Planet
The two natural satellites, or moons, of Mars are Phobos (fear) and Deimos (terror). They are named after the horses which pulled the chariot of Mars, the god of war in the mythology of Ancient Greece.
Phobos takes less than eight hours to orbit Mars and gets slightly closer every time it does so. Scientists predict that in about 100 million years time it will either be ripped apart by the gravitational force or will crash onto the surface of Mars.
(a) Suggest how scientists have arrived at their prediction of about 100 million years.
.....................................................................................................................................
.....................................................................................................................................(2)
(b) The centripetal force on Phobos is gradually changing as it orbits Mars.
Is the force increasing or decreasing?
.....................................................................................................................................
Explain your answer.
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................(2)
(c) Scientists expect that the mass of Mars and the mass of Phobos will not increase.
Explain what will happen to the gravitational force on Phobos as it orbits Mars.
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................(2)
(Total 6 marks)
Q9. (a) Complete the following sentence by drawing a ring around the correct line in the box.
A racing car can accelerate by changing
its direction only
its speed only
either its direction or its speed
.
(1)
(b) A racing car moves round a circular part of a racetrack.
A force acts on the racing car. The force is towards the centre of the circular part of the racetrack.
Complete the following sentences by drawing a ring around the correct line in each of the boxes.
(i)
The force is caused by
electrostatics
friction
gravity
.
(1)
(ii)
centripetal force
The force is a circular force
perpendicular force
.
(1)
(iii) If another racing car has a greater mass and travels at the same speed
around the same racetrack, then the force will need to
decrease
stay the same
increase
.
(1)
(iv)
When the racing car goes faster, the force will need to
decrease
stay the same
increase
.
(1)
(c) This is an item from a newspaper.
No to racetrack planAt last night’s meeting, one local resident said, “The racetrack will be noisy but motor racing leads to safety improvements in all our cars.’’
“We’ll need better brakes. Motor racing encourages speeding and leads to more accidents’’, said another.
Most of the residents were against the plan to build a racetrack.
Do you agree with most of the residents?
Put a tick ( ) in the box next to your answer and explain.
Yes No Not sure
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................(2)
(Total 7 marks)
Q10.(a) The diagram shows a satellite moving in a circular orbit above the Earth.
A centripetal force acts on the satellite, causing it to accelerate.
(i) Use a word from the box to complete the sentence.
friction gravity tension
The centripetal force on the satellite is provided by ........................... .(1)
(ii) In what direction does the satellite accelerate, A, B or C?
.......................................(1)
(iii) When the satellite accelerates in a circular orbit its speed does not change.
Draw a ring around the correct answer in the box to complete the sentence.
direction.
When the satellite accelerates there is a change in its distance from the Earth.
kinetic energy.
(1)
(b) The electrical systems on the satellite can be powered by rechargeable batteries.
One fully charged 4 volt battery stores 216 000 coulombs of charge.
Calculate the energy, in joules, available from one fully charged battery.
........................................................................................................................
........................................................................................................................
........................................................................................................................
Energy available = ............................................... J(2)
(c) Batteries to be used on a satellite must not discharge by more than 15% when left unused for three years.
Scientists test new types of battery by charging them to 4 volts and then storing them at 37 °C for several years. The potential difference of the battery is measured every month.
The graph shows the data obtained for one type of battery.
(i) Use the graph to calculate the time taken, in years, for the potential difference of this battery to drop by 15%.
...............................................................................................................
...............................................................................................................
...............................................................................................................
Time taken = .............................. years(2)
(ii) Use your answer from (c)(i) to explain whether this battery is suitable for use on a
satellite.
...............................................................................................................
...............................................................................................................(1)
(d) There are now thousands of satellites in orbit around the Earth. A student used the Internet to find information about three of them.
The table shows the information found by the student.
Satellite Height of the orbit above theEarth in kilometres
Orbital speed inkilometres per hour
K 705 27 500
L 20 200 13 900
M 35 800 11 100
A student concluded that the greater the height of the satellite the slower the orbital speed.
Any conclusion drawn from the data in the table might not be valid for all satellites.
Suggest reasons why.
........................................................................................................................
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........................................................................................................................
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........................................................................................................................
........................................................................................................................(3)
(Total 11 marks)
Q11. The fairground ride called ‘The Rotor’ is a large cylinder which rotates. When the cylinder reaches its maximum speed the floor drops away and the riders inside the cylinder are left against the cylinder wall.
(a) Explain how the cylinder is rotating at a constant speed but at the same time the riders inside the cylinder are accelerating.
........................................................................................................................
........................................................................................................................
........................................................................................................................
........................................................................................................................
........................................................................................................................
........................................................................................................................(3)
(b) In which direction do the riders accelerate?
........................................................................................................................(1)
(c) What name is given to the resultant force that causes the riders to accelerate?
........................................................................................................................(1)
(d) At the end of the ride the floor goes back into place and the cylinder slows down and stops.
How does the resultant force on the riders change as the cylinder slows down?
........................................................................................................................
........................................................................................................................(1)
(Total 6 marks)
Q12. The picture shows a fairground carousel.
The diagram shows the position of one child, at one point in the ride, viewed from above.
Picture Diagram
Draw a ring around the correct answer to complete the following sentences.
(a) The resultant force needed to keep the child moving in a circular path is
centripetal
circular
gravitational
called the force.
(1)
A.
B.
C.
(b) The resultant force on the child acts in the direction
(1)
(c) At the end of the ride, as the carousel slows down, the resultant force on
decreases.
stays the same.
increases.
the child
(1)(Total 3 marks)
Q13. The hammer throw is an athletic event.
The athlete throws a heavy metal ball attached by a wire to a handle.
(a) The hammer thrower swings the hammer round in a circle before letting go.
He swings the hammer slowly at first and then faster.
Complete the following sentence by drawing a ring around the correct word or line in the box.
As the speed of the swing increases, the centripetal force on the
decreases.
hammer does not change.
increases.
(1)
(b) The diagram shows an overhead view of a hammer thrower swinging the hammer anticlockwise in a circle.
(i) In which direction, A, B, C or D, does the centripetal force act on the hammer?
(1)
(ii) Complete the following sentence by drawing a ring around the correct line in the box.
air resistance.
The centripetal force is provided by the gravitational force.
tension in the wire.
(1)
(iii) At the instant shown in the diagram above, the athlete lets go of the handle.
In which direction, A, B, C or D, does the hammer move?
(1)(Total 4 marks)
Q14. The drawing shows a skateboarder moving in a circular path.
• Centre of circular path
(a) (i) What is the name of the resultant force which allows the skateboarder to move in a circular path?
Draw a ring around your answer.
centripetal force gravitational force weight(1)
(ii) In which direction, A, B or C, does this resultant force act on the skateboarder?
Write your answer, A, B or C, in the box.
(1)
(b) Another skateboarder has a smaller mass.
Complete the following sentences by drawing a ring around the correct line in each box.
(i) She uses the same part of the ramp at the same speed.
The force which allows her to move in a circular path will need
decrease.
to
stay the same.
increase.
(1)
decrease.
(ii)
If she goes faster, this resultant force will need to stay the same.
increase.
(1)
(c) On their website, the managers of a skateboard park give the following information about some of the ramps where skateboarders move in a circular path.
Name of ramp Inside radius of the rampin metres
Bull pit 6
Dragon’s den 11
Tiger cage 8
Witch’s cauldron 7
A skateboarder uses each ramp at the same speed.
Name the ramp where the resultant force on the skateboarder will need to be the greatest.
................................................................
Explain the reason for your answer.
........................................................................................................................
........................................................................................................................(2)
(Total 6 marks)
Q15.The diagram shows the apparatus used by two students to find out how the centripetal force acting on an object affects the speed of the object.
(a) (i) In which direction does the centripetal force act on the rubber bung?
...............................................................................................................(1)
(ii) In this investigation, what provides the centripetal force?
...............................................................................................................
...............................................................................................................(1)
(b) One student swung the rubber bung around in a circle at constant speed. The second student timed how long it took the rubber bung to complete 10 rotations. The students then calculated the speed of the rubber bung, using the radius of the circle and the time to complete one rotation. The students repeated this for several different values of centripetal force.
(i) During the investigation, the radius of the circle and the mass of the rubber bung were not changed.
Explain why.
...............................................................................................................
...............................................................................................................
...............................................................................................................
...............................................................................................................(2)
(ii) One of the variables in this investigation was the time taken by the rubber bung to complete 10 rotations.
Which two words can be used to describe this variable?
Draw a ring around each of your two answers.
continuous control dependent independent(1)
(iii) The students timed 10 rotations of the rubber bung, rather than just one rotation.
Suggest why.
...............................................................................................................
...............................................................................................................(1)
(c) The graph shows the students’ data.
There is a relationship between the speed of an object moving in a circle and the centripetal force acting on the object.
What conclusion about this relationship can the students make from their data?
........................................................................................................................
........................................................................................................................(1)
(d) The diagram shows a satellite in a circular orbit above the Earth.The satellite is part of the global positioning system (GPS).The satellite orbits the Earth twice every 24 hours.
(i) What provides the centripetal force needed to keep the satellite in its orbit around the Earth?
...............................................................................................................(1)
(ii) Is this satellite in a geostationary orbit?
Draw a ring around your answer. Yes No
Give a reason for your answer.
...............................................................................................................
...............................................................................................................(1)
(Total 9 marks)
Q16.The London Eye is one of the largest observation wheels in the world.
© Angelo Ferraris/Shutterstock
The passengers ride in capsules. Each capsule moves in a circular path and accelerates.
(a) Explain how the wheel can move at a steady speed and the capsules accelerate at the same time.
........................................................................................................................
........................................................................................................................
........................................................................................................................(2)
(b) In which direction is the resultant force on each capsule?
........................................................................................................................(1)
(c) The designers of the London Eye had to consider three factors which affect the resultant force described in part (b).
Two factors that increase the resultant force are:
• an increase in the speed of rotation
• an increase in the total mass of the wheel, the capsules and the passengers.
Name the other factor that affects the resultant force and state what effect it has on the resultant force.
........................................................................................................................
........................................................................................................................(1)
(Total 4 marks)
Q17.The hammer throw is an athletic event.
The athlete throws a heavy metal ball attached by a wire to a handle.
(a) The hammer thrower swings the hammer round in a circle before letting go.
He swings the hammer slowly at first and then faster.
Complete the following sentence by drawing a ring around the correct word or line in the box.
As the speed of the swing increases, the centripetal force on the
decreases.
hammer does not change.
increases.
(1)
(b) The diagram shows an overhead view of a hammer thrower swinging the hammer anticlockwise in a circle.
(i) In which direction, A, B, C or D, does the centripetal force act on the
hammer? (1)
(ii) Complete the following sentence by drawing a ring around the correct line in the box.
air resistance.
The centripetal force is provided by the
gravitational force.
tension in the wire.
(1)
(iii) At the instant shown in the diagram above, the athlete lets go of the handle.
In which direction, A, B, C or D, does the hammer move? (1)
(Total 4 marks)
Q18.The diagram shows a ‘G-machine’. The G-machine is used in astronaut training.
The G-machine moves the astronaut in a horizontal circle.
(a) When the G-machine is rotating at constant speed, the astronaut is accelerating.
State the name and direction of the force causing the astronaut to accelerate.
Name of force ................................................................................................
Direction of force ...........................................................................................
........................................................................................................................(2)
(b) The force causing the astronaut to move in a circle is measured.
The graph shows how the speed of the astronaut affects the force causing the astronaut to move in a circle for two different G-machines.
The radius of rotation of the astronaut is different for each G-machine.
Speed in metres per second
(i) State three conclusions that can be made from the graph.
1 ............................................................................................................
...............................................................................................................
2 ............................................................................................................
...............................................................................................................
3 .............................................................................................................
...............................................................................................................(3)
(ii) The speed of rotation of G-machine 1 is increased from 20 m/s to 40 m/s.
Determine the change in force on the astronaut.
...............................................................................................................
Change in force = ............................................................ N(1)
(c) Each G-machine is rotated by an electric motor. The diagram shows a simple electric motor.
(i) A current flows through the coil of the motor.
Explain why side A of the coil experiences a force.
...............................................................................................................
...............................................................................................................
...............................................................................................................
...............................................................................................................(2)
(ii) Draw arrows on the diagram to show the direction of the forces acting on side A of the coil and side C of the coil.
(1)
(iii) When horizontal, side B experiences no force.
Give the reason why.
...............................................................................................................
...............................................................................................................(1)
(d) While a G-machine is rotating, the operators want to increase its speed.
What can the operators do to make the G-machine rotate faster?
........................................................................................................................
........................................................................................................................(1)
(e) The exploration of space has cost a lot of money.
Do you think spending lots of money on space exploration has been a good thing?
Draw a ring around your answer.
Yes No
Give a reason for your answer.
........................................................................................................................
........................................................................................................................(1)
(Total 12 marks)
Q19.The diagram shows a ‘G-machine’. The G-machine is used in astronaut training.
The G-machine moves the astronaut in a horizontal circle.
(a) In which direction, A, B or C, does the centripetal force on the astronaut act?
Write your answer in the box.
(1)
(b) The centripetal force on the astronaut is measured.
Graph X shows how the centripetal force is affected by the speed of rotation.The radius of rotation is kept the same.
Speed of rotationin metres per second
(i) Use Graph X to determine the centripetal force on the astronaut when rotating at a speed of 30 metres per second.
Centripetal force = .............................. newtons(1)
(ii) Complete the following sentence to give the conclusion that can be made fromGraph X.
Increasing the speed of rotation of a G-machine will ................................................
the centripetal force on the astronaut.(1)
(iii) Graph Y shows how the centripetal force is affected by the radius of rotation, when the speed of rotation is kept the same.
Radius of rotationin metres
Complete the following sentence to give the conclusion that can be made fromGraph Y.
The greater the radius of rotation, the ......................................... the centripetal force
on the astronaut.(1)
(c) The G-machine is rotated by an electric motor. The diagram shows a simple electric motor.
The following statements explain how the motor creates a turning force. The statements are in the wrong order.
M – The magnetic field interacts with the magnetic field of the permanent magnets.
N – A magnetic field is created around the coil.
O – The power supply applies a potential difference across the coil.
P – This creates a force that makes the coil spin.
Q – A current flows through the coil.
Arrange the statements in the correct order. Two of them have been done for you.
(2)
(d) The electric motor produces a turning force.
Give two ways of increasing the turning force.
1 .....................................................................................................................
........................................................................................................................
2 .....................................................................................................................
........................................................................................................................(2)
(e) Draw a ring around the correct answer to complete the sentence.
It costs a lot of money to send astronauts into space.
an economic
This is an environmental issue.
a social
(1)(Total 9 marks)
Q20.The diagram shows a satellite moving in a circular orbit around the Earth.
There is a centripetal force acting on the satellite.
(a) Which arrow, A, B, C or D, shows the direction of the centripetal force? (1)
(b) Draw a ring around the correct answer to complete each sentence.
The speed of the satellite increases. For the satellite to stay in the same orbit
the centripetal force on the satellite must
decrease.
stay the same.
increase.
The radius of the orbit increases. For the satellite to stay at the same speed
the centripetal force on the satellite must
decrease.
stay the same.
increase.
(2)
(c) A satellite in a geostationary orbit always stays above the same point on the surface of the Earth.
These satellites:
• are used for communications
• are in a fixed orbit at 36 000 km above the surface of the Earth
• complete one orbit in 24 hours.
The table shows three geostationary satellites, E, F and G, and their masses.
Satellite Mass of satellite in kg Launch date
E 1200 1978
F 1500 1984
G 3500 2011
(i) Describe a pattern shown in the table.
................................................................................................................
................................................................................................................(1)
(ii) Which satellite has the greatest centripetal force acting on it?
Give a reason for your answer.
................................................................................................................
................................................................................................................
................................................................................................................(2)
(iii) Mass is the only thing that affects the force acting on a geostationary satellite.
Explain why.
................................................................................................................
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................................................................................................................
................................................................................................................(2)
(Total 8 marks)
M1. (i) towards Earthfor 1 mark
1
(ii) gravityfor 1 mark
1
(iii) changes directionfor 1 mark
1
(iv) polar orbit;closer
for 1 mark each2
(v) speed constant (1)mass constant (1)
for 1 mark each2
[7]
M2. (a) (i) arrow from centre of the ball and at right angles to the stringand in the correct direction
arrow should point to the student’s beltaccept free-hand ‘straight’ line do not accept curved line
1
(ii) increaseaccept ‘be stronger / bigger’
1
increaseaccept ‘be stronger / bigger’
1
increaseaccept ‘be stronger / bigger’
1
(b) speedvelocitydirection
all three correctany two correct for 1 markotherwise 0 marks
2
(c) (i) centripetalaccept ‘centripedal’ and other minor misspellingsdo not accept anything which could be ‘centrifugal’
1
(ii) gravityaccept ‘weight’accept ‘force of attraction due to mass(es) (of the Moon and the Earth)’
1
(iii) electron(s)1
(iv) electrostaticaccept ‘electrical’do not accept just ‘centripetal’
1[10]
M3. (a) converging1
image1
object1
image1
object1
shorter1
(b) (i) (Earth’s) gravityaccept centripetal accept minor misspellings, however, do not credit any response which could be ‘centrifugal’
1
(ii) to(wards) (the centre of the) Earthallow inwards do not accept downwards
1
(c) (i) either
friction (force) or centripetal forceallow grip
1
between the tyres / wheels and (the surface of) the roadallow on the tyres / wheels or towards the centre of the bend / arc / circle
1
(ii) mass or speed or momentumallow weight allow velocity
1
radius / diameterdo not credit ‘curvature’ or ‘circumference’
1
(d) centripetalaccept minor misspellings (see above)
1[13]
M4. (a) any two ideas:
• (acceleration occurs when) the direction (of each capsule) changes
• velocity has direction
• acceleration is (rate of) change of velocity2
(b) to(wards) the centre (of the wheel)1
(c) centripetalallow minor misspellings but do not credit a response which could be ‘centrifugal’
1
(d) the greater the radius / diameter / circumference (of the wheel)the smaller the (resultant) force (required)
accept ‘the size’both parts required for the markaccept converse
1[5]
M5. (a) (i) P1
(ii) the child’s grip / hold / pull (on the roundabout / bar / rail)or ‘the tension in the child’s arms’accept ‘the child’s muscles’accept ‘friction between the child and the roundabout’do not accept just ‘friction’
1
(iii) increasesaccept any unambiguous indication that this ending has been selected
1
(b) (i) 360 (Nm)credit either 240 × 1 ½or 240 × 1.5 with 1 mark
2
(ii) move to(wards) the left / to(wards) the / his endor move away from the centre / pivot / axis (of rotation)or move away from the girl / the child / his daughter
1
(c) (i) C1
(ii) friction / grip of the car / tyres / wheels (on the road)do not accept just ‘friction / grip’
1[8]
M6. (a) tensionaccept any unambiguous method of indication eg it’s underlined orticked
1
(b) (i) speed of the ball is increased1
(ii) the direction of the ball1
(c) centripetalaccept any unambiguous method of indicationeg it’s underlined or ticked
1[4]
M7. (a) (i) directionaccept any unambiguous indication
1
(ii) centripetalaccept any unambiguous indication
1
(b) Aaccept any unambiguous indication
1
(c) mass of the passengers is greateraccept any unambiguous indication
1[4]
M8. (a) (from present/recent) data/evidence/observations of (the rate of change in)Phobos’/the moon’s orbit (1)
or appropriate example of data (1)and its correct use (1)
(and) continued/extended/extrapolated(the pattern/trend for the next 100 million years) (1)example (present) distance from Phobos to Mars (1) ÷ (average) rate of approach (1)
2
(b) (it is) increasing (1)
Phobos/the moon will be nearer (to Mars) (1)or the radius/circumference/diameter of the orbit of Phobos/the moon will decrease/be lessonly credit 2nd mark if the first mark is correct
2
(c) it will increase/be more (1)
(because) Phobos/the moon will get/be closer to Mars/the planet (1)only credit 2nd mark if the first mark is correctnote part(s) of this response may be included as the answer to part (b)
read both before marks are awarded2
[6]
M9. (a) either its direction or its speed1
(b) (i) friction1
(ii) centripetal1
(iii) increase1
(iv) increase1
(c) examples
(yes) noisy (1)
disturbs people living nearby (1)
(yes) encourages people to drive fast (1) which makes (road) accidents more serious/likely (1)
(no) leads to improvements in safety features (1) such as better brakes (1)
(don’t know) noisy (1) but new tyres have a better grip (1)whichever box has been ticked, the mark(s) is/are for an appropriate responsenote, accept responses which assume that the public may use the racetrack
2[7]
M10.(a) (i) gravity1
(ii) C1
(iii) direction1
(b) 4 × 216 0001
864 000 (J)correct answer with or withoutworking gains 2 marks
1
(c) (i) 15% of 4.0 = 0.60.6 or 3.4 scores first mark
1
or
85% of 4.0 = 3.4
(from graph, time is therefore) 1.05 (years)allow range 1.0 to 1.1 yearsallow 2 marks for an answer in range 1.0 to 1.1
1
(ii) not suitable because answer in (c)(i) is less than 3 yearsecf from incorrect answer in (c)(i)
1
(d) there is not enough / insufficient dataaccept there are only three pairs of data
1
the conclusion is only valid for satellites in the range shown1
the Internet is not always a reliable sourceinsufficient data for the intervening heights scores 2 marks
1[11]
M11. (a) the direction of the riders is constantly changing1
therefore the velocity of the riders is changing1
and because acceleration is the rate of change of velocitythe acceleration is changing
1
(b) to(wards) the centre (of the cylinder / rotor)1
(b) centripetal1
(b) it is reduced1
[6]
M12. (a) centripetal1
(b) B1
(c) decreases1
[3]
M13. (a) increases1
(b) (i) B1
(ii) tension in the wire1
(iii) C1
[4]
M14. (a) (i) centripetal forceaccept any unambiguous correct indication
1
(ii) B1
(b) (i) decreaseaccept any unambiguous correct indication
1
(ii) increaseaccept any unambiguous correct indication
1
(c) Bull pit1
smallest (inside) radiusaccept smallest diameter / circumference
1[6]
M15. (a) (i) towards the centre of the circleaccept inwardsaccept a correct description‘along the string’ is insufficient
1
(ii) tension (in the string)accept pull of the string‘the string’ is insufficient
orweight (on the end of the string)‘the student’ is insufficient‘turning action’ is insufficient
1
(b) (i) each may (also) affect the speedaccept results for speed
1
so only one independent variableaccept only one variable affects dependent variable‘fair test’ is insufficient‘they are control variables’ is insufficient
1
(ii) continuousboth required
dependent1
(iii) reduces (absolute) timing error (for one rotation)accept too fast to time one
orincreases / improves reliability / accuracy (for one rotation)
ignore checking for anomalous results
to work out an average is insufficient1
(c) speed increases with centripetal forceaccept positive correlationdo not accept proportional
1
(d) (i) gravitational pull (of the Earth)accept gravity
1
(ii) Noboth parts required – however this may have been subsumed within the reason
geostationary orbits once every 24 hoursaccept a correct comparative description
1[9]
M16.(a) any two from:
• (acceleration occurs when) the direction (of each capsule) changes
• velocity has direction
• acceleration is (rate of) change of velocity2
(b) to(wards) the centre (of the wheel)1
(c) the greater the radius / diameter / circumference (of the wheel) the smaller the (resultant) force (required)
accept ‘the size’ for radiusboth parts required for the mark
1[4]
M17.(a) increases1
(b) (i) B1
(ii) tension in the wire1
(iii) C
1[4]
M18.(a) centripetal (force)allow tension (between astronaut and seatbelt)
1
towards the centre (of the G-machine / circle)do not accept towards the centre of the Earthallow inwards
1
(b) (i) the greater the speed (of a centrifuge), the greater the forceanswers must be comparativeaccept velocity for speedaccept positive correlation between speed and forcespeed and force are not proportional – treat as neutral
1
the smaller the radius, the greater the force (at a given speed)allow (G machine) 1 has / produces a greater force (thanG machine 2 ) at the same speedmust be comparative, eg a small radius produces a large force = 0 marks on own
1
as the speed increases the rate of change in force increasesaccept force is proportional to the square of the speedordoubling speed, quadruples the forceaccept any clearly correct conclusion
1
(ii) 12000 (N)
or
12 k(N)1
(c) (i) the current (in the coil) creates a magnetic field (around the coil)accept the coil is an electromagnet
1
so the magnetic field of the coil interacts with the (permanent) magnetic field of the magnets (producing a force)
accept the two magnetic fields interact (producing a force)if no marks scored an answer in terms of current is perpendicular to the (permanent) magnetic field is worth max 1 mark
1
(ii) vertically downwards arrow on side A
one arrow insufficient
and
vertically upwards arrow on side C1
(iii) the current is parallel to the magnetic fieldallow the current and magnetic field are in the same directionallow it / the wire is parallel to the magnetic field
1
(d) increase the current / p.d. (of the coil)accept decrease resistanceaccept voltage for p.d.accept increase strength of magnetic field / electromagnet
1
(e) yes with suitable reasonorno with suitable reason
egyes – it has increased our knowledgeyes – It has led to more (rapid) developments / discoveries (in technology / materials / transport) accept specific examplesno – the money would have been better spent elsewhere on such things as hospitals (must quote where, other things not enough)no mark for just yes / noreason must match yes / no
1[12]
M19.(a) A1
(b) (i) 9000an answer of 9 k(N) gains 1 mark
1
(ii) increaseaccept other comparative terms, eg give a biggeraffect / change is insufficient
1
(iii) smalleraccept other comparative terms, eg less
1
(c) Q N Mall three in correct boxesone statement in correct box gains 1 mark
2
(d) any two from:
• increase the current / p.d. (supplied to the coil)accept reduce the resistance of the coil or increase cross sectional area of wireaccept more cells / batteries or turn up the power supplyincrease power is insufficient
• increase number of turns (on the coil)
• increase the area (of the coil)accept increase the width of the coilincrease width / size is insufficient
• increase the (strength of the permanent) magnetic fieldaccept move the magnets closer to the coilaccept use stronger magnetsdo not accept use larger magnets
2
(e) an economic1
[9]
M20.(a) C1
(b) increase1
decrease1
(c) (i) modern satellites are heavieraccept converse
1
(ii) G1
greatest massaccept heaviest, dependent mark
1
(iii) radius is fixedaccept diameter / circumference / distance from centreaccept length and time of orbit is fixed
1
(so) speed is fixedaccept acceleration is constantdo not allow velocity is fixed
1[8]
E1. The direction and cause of the force were well known but the effect on the velocity was not. The correct orbit was frequently chosen but many missed the simple answer to part (v), namely the mass and speed remain constant.
E2. Part (a)(i) was only answered correctly by a minority of candidates. In part (a)(ii) many seemed to have convinced themselves that the answers could not all be the same. The most common mistake was to conclude that, if the radius is smaller, the force needed will also be smaller.
Only a minority gained both marks. Candidates often did not seem to have a clear understanding of the Moon’s circular motion nor of the difference between speed and velocity.
In part (c) the answers to parts (ii) and (iii) were usually correct but ‘centripetal’ in part (i) was less well known, and in part (iv) ‘electrostatic’ was almost never seen.
E3. (a) Many candidates obtained full marks in this part.
(b) (i) Most candidates correctly gave ‘gravity’ or ‘gravitational attraction’ in this part.
(ii) Not all the candidates who gave the correct answer in part (b)(i) were able to give the correct direction in this part. ‘Towards the Sun’ and ‘clockwise’ were sometimes suggested and the examiners did not consider that ‘downwards’ was an appropriate response in the context of the question.
(c) (i) ‘Friction’ was rarely suggested in this part although, if it was, then it was usually correctly located between the tyres and the road surface.
(ii) Most candidates correctly indicated that the force would be greater if the mass, or the speed, of the car was greater, but very few could express themselves correctly and describe a tighter bend. Many candidates suggested ‘angle’ or ‘curve’ for the second word and if these words convey any meaning here, it is the opposite of what might have been intended. The word ‘diameter’ or ‘radius’ was hardly ever seen.
(d) Only a very small minority gave the correct response to this part. Of the incorrect responses, ‘orbit’ was the most common.
E4. (a) A minority of candidates realised that, as velocity is speed in a particular direction and the direction of each moving carriage is changing then each moving carriage must be accelerating.
(b) Only a minority of candidates stated that the acceleration is towards the centre of the wheel.
(c) Most candidates correctly identified the resultant force as a ‘centripetal’ force.
(d) Examiners were pleased to note that a significant proportion of candidates were able to identify the other factor as the radius of the wheel and were able to state that the greater the radius the smaller the resultant force.
E5. (a) (i) Slightly fewer than half the candidates could identify P as the direction of the centripetal force.
(ii) Very few candidates realised that the centripetal force was provided by the girl’s grip.
(iii) Three quarters of candidates identified that if the speed of the roundabout increases that the centripetal force increases.
(b) (i) This question was well answered with more than 80 % of candidates gaining the 2 marks available.
(ii) Two thirds of candidates were able to identify the direction in which the father moves correctly.
(c) (i) Over 80 % of candidates gave the correct answer and therefore gained a mark.
(ii) Very few candidates could identify the friction between the tyres and the road as the source of centripetal force.
E6. (a) Most candidates correctly selected ‘tension’.
(b) (i) More candidates chose the incorrect response ‘the string is made longer’ than candidates who chose the correct response ‘the speed of the ball is increased’.
(ii) Only a small minority of candidates correctly associated ‘acceleration’ with a change in direction.
(c) A large majority of candidates correctly selected ‘centripetal’.
E7. (a) (i)(ii) Just over half the candidates correctly linked acceleration with change in direction and two thirds were able to identify the resultant force as centripetal.
(b) A minority of candidates gave the correct direction for this force.
(c) About half of the candidates knew that it will need to be greater if the mass of the passengers is greater.
E8. (a) Most candidates realised that the scientists must have made observations and gave an example of the data, such as the rate at which Phobos is approaching Mars, they would use to help them make their estimate of 100 million years. However, only a minority were able to gain the second mark by explaining how the data could be used.
(b) Most candidates knew that the centripetal force must be increasing and correctly explained this by stating that the radius of its orbit is decreasing or that Phobos is getting closer to Mars.
(c) Most candidates realised that the explanation is that the gravitational force will increase as the moon gets closer to Mars.
E9. (a)(b) Less than half the candidates recognised that a racing car can accelerate by (b)changing either its direction or its speed and identified friction as the force acting on a racing car and towards the centre of a circular part of the track.However, nearly all recognised that friction is acting as the centripetal force and most knew that it would be increased if the racing car had a greater mass and travelled faster.
(c) Most candidates gained full marks on this item. Some candidates thought that members of the public would be able to use the racetrack and the mark scheme makes it clear that this idea is acceptable.
E13. (a) Most candidates knew how speed affects centripetal force.
(b) (i) Just over half of the candidates knew the direction of the force.
(ii) About half of the candidates correctly identified the source of the force although almost as many candidates thought it was provided by gravity.
(iii) About three fifths of candidates knew in which direction the hammer would move should the force be removed, with most of the wrong answers giving the direction as D.
E14. (a) (i) Most candidates identified the force as centripetal force.
(ii) Just under a half of the candidates knew in which direction the centripetal force acts.
(b) (i) Candidates were uncertain as to the effect of mass on a force. Just under a half of candidates thought that a lower mass will cause an increase in force.
(ii) Two-thirds of candidates realised that an increased speed resulted in increased force.
(c) Few candidates knew the effect of radius on centripetal force, with only a tenth of candidates naming the correct ramp and giving the correct reason for that choice.
E15. (a) (i) A third of students knew the direction of the centripetal force.
(ii) Nearly half of students were able to give the provider of the centripetal force.
(b) (i) Very few students were able to give a complete answer as to why the radius of the circle and mass of the rubber bung were kept constant. However nearly one fifth of students did score 1 mark.
(ii) Disappointingly only a third of students could identify the two words to describe the chosen variable.
(iii) Almost ahalf of students could explain why 10 rotations were timed rather than 1. However some students had clearly not read the question carefully and seemed to think that 10 separate timings had been made.
(c) This question was well done with most students giving the correct relationship between the two variables. It was good to notice that very few used the word ‘proportional’ this year.
(d) (i) Over four fifths of students realised that the centripetal force was provided by the gravitational pull of the earth.
(ii) Fewer than one fifth of students realised that the satellite described was not
geostationary and gave an acceptable reason.
E16.(a) Some students gained one mark for the change of direction; only a very small number of the students gained both marks and, of these, most had given all three of the marking points. There were worrying responses about the downward capsules travelling faster than the upwards ones due to gravity.
(b) Half the students gave the correct answer.
(c) The most frequent answer was “wind” or “wind resistance”; less than a quarter of the students gained the mark.
E17.This question on circular motion was an unusual scenario to which a significant number of students had difficulty relating the facts. Less than half identified the centripetal force as being supplied by the tension in the wire. Almost all the rest thought it was the gravitational force. Just over half knew that the direction of the force was towards the centre of motion. The other two parts were answered better.
E18.(a) The majority of candidates gained both marks on this question. Common errors were “centrifugal” or “centripedal”.
(b) (i) Very few candidates scored all 3 marks, but half of the candidates scored 2. Some mistakenly stated that force changed the speed, rather than understanding that the speed of rotation affected the centripetal force on the astronaut.
(ii) Two thirds of candidates calculated the correct answer.
(c) (i) The majority of responses gained a mark of zero. Use of correct terminology, e.g. the permanent magnetic field interacting with the magnetic field produced by the current, should be stressed to candidates.
(ii) Only a quarter of candidates gained this mark where Fleming’s Left Hand Rule had to be applied. Some failed to gain the mark as they drew in how the coil would rotate, rather than the direction of the forces.
(iii) A quarter of candidates gained this mark. There were a lot of incorrect answers showing the misconception that the upwards and downward forces were equal and opposite.
(d) Two thirds of candidates gained this mark. Of the candidates who did not score, many failed to realise that what was required was an immediate change that the operators could make, or were too brief with their answer “increase the supply”.
(e) This question tested the societal aspects of scientific evidence. Many coherent answers were produced, with the majority of the responses gaining the mark. At times answers were too brief, “the money would be better spent elsewhere”, rather than stating exactly where (e.g. medical care / hospitals). Some answers looked at possible future benefits, rather than the benefits achieved so far.
E19.(a) Half of the candidates correctly identified the direction of the centripetal force.
(b) The vast majority were able to score all the marks in (b)(i), (b)(ii) and (b)(iii).
(c) About two thirds of candidates correctly placed all three letters; but a significant minority failed to gain marks here.
(d) Around half the candidates scored both marks, but a common mistake was referring to the power supply rather than an increase in p.d. or current. Some candidates failed to score by referring to the use of ‘bigger’ magnets or a ‘bigger’ magnetic field.
(e) The vast majority of candidates gained this mark.
E20.(a) Nearly all the students knew the direction of the centripetal force acting on a satellite.
(b) Less than half of the students were able to state the effect on the centripetal force of a change of speed or orbit.
(c) (i) Nearly all students were able to describe the pattern of data given in a table for mass and launch date of some satellites.
(ii) Nearly all students knew that for satellites in a fixed orbit, the one experiencing the greatest centripetal force was the one with the greatest mass.
(iii) About one-fifth of the students could explain why only mass affects the force acting on satellites in a fixed orbit.