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For each of the questions, there are four possible
choices. Choose the one you consider conect andrecord your choice.
IVs l. A block of ice is sliding at a constant speed
before moving up a smooth slope as shown.
What are the changes in its kinetic energy and
gravitational potential energy as it is sliding up
the slope?
constant speed-----------)
4. Abox of mass 2 kg is being pushed horizontallyon a smooth surface by a l0 N force for 6 m.
What is the work done on the box by the l0 Nforce?
10N I
----------t 'I2
+---- ----->6m
B 48JD I2OJ
U
\Vg
MCI
kg
A I2JC 6OJ (
lce
5. Abox of mass 2 kg is being pushed horizontally
on a rough surface by a l0 N force for 6 m.
Given that the friction between the box and the
surface is 4 N, what is the work done on the box
by the l0 N force?
+------o-g------>
Kineticenergy
A increase
B increase
C decrease
D decrease
Gravitationalpotential energy
increase
decrease
increase
decrease (
10N 2ke i
t-----r
U A 24tC 6OJ
<-4N
B 36JD IZOJ
d
2. A car is accelerating up a slope. What are the
changes in its kinetic energy and gravitationalpotential energy as it is moving up the slope?
Kinetic Gravitationalenergy potential energy
A increase increase
B increase decrease
C decrease increase
D decrease decrease ( )
3. Abox is being pushed horizontally on a smooth
surface by a l0 N force for 6 m. What is the
work done on the box by the 10 N force?
tON r-----l l--------lzi ll+---- ----->6m
A O.6J B I.1JC I6J D 6OJ
6. Abox of mass 2 kg is being pushed horizontallyon a smooth surface by a l0 N force for 6 m.
What is the work done on the box by the weightofthe box? (g = 10 N kg-')
2ke :
+---- ------)6m
A OJ B I2JC 6OJ D I}OJ )
(
39 Unit 7 Energ, Work and Power
UNIT 7
Energy, Work and PowerMechanics
Theme 2
I*I)
()
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7 . Abox of mass 2 kg is being pushed horizontally
by a l0 N force for 60 cm along the floor.
During the first 20 cm, the friction between the
box and the floor is 4 N, and the friction for the
rest of the distance is negligible. What is the
work done on the box by the l0 N force?
A2J B3J C4I D6J ( )
8. A box of mass 2 kg is moving at a constant
speed of 3 m s-r. What is the kinetic energy ofthe box?
A2J B3J C9J Dl8J( )
9. A box of mass 500 g is moving at a constant
speed of 72 km/h. What is the kinetic energy
of the box?
A 5J B 1OOJ
c r296J D r296000J ( )
10. A box of mass 2 kg increases its speed from3 m s I to 7 m s-r. What is the increase in kineticenergy?
A4I Bl6J C40J D32I ( )
11. A box of mass 2 kg is lifted vertically upwards
by 3 m. Given that the acceleration due togravity is 10 m/s2, what is the gravitationalpotential energy gained by the box?
A0.6J86.71 Cl5J D60J( )
12. A box of mass 2 kg is lifted diagonally frompoint A to point B as shown. Given that the
acceleration due to gravity is 10 m s 2, what is
the gravitational potential energy gained by the
box?
B
d
U
5m,'3
A 2OJ
C 8OJ
4m
B 6OJ
D IOOJ ()
a
U
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A
13. There are 3 paths leading to the top of the hill as
shown. Assuming that the friction of the ground
is negligible, which of the following statement
is true?
path A(10
Path Bm)
A Path C requires most energy to reach the
top.
B Path B requires the least energy to reach the
top.
C Path B requires more energy than path A toreach the top.
D All three paths require the same amount ofenergy to reach the top. ( )
14. A box of 2 kg mass moves up a ramp frompoint A to point B at a constant speed. Giventhat the surfaces are smooth (frictionless), whatis the gain in the potential energy by the box?(g=10Nkg-')
B
6m
5m m4
3m
A 8OJ
C 2OOJ
B lOOJ
D 22OJ ()
path C(12 m)
m
40 Unit 7 Energy, Work and Power
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15. A pendulum bob pivots at point P, startsswinging from point S. Assuming that there is
no loss ofenergy to the surrounding, at whichposition will the bob next come to a momentary
rest?
P
D
Cs
B
A ()
d
16. Three different stones are being lifted from the
ground level to different heights on differentplanets as given below.
Case 1: A 250 g stone lifted to l0 m on Earth
Case 2: A 6 kg stone lifted to 2 m on the
MoonCase 3: A 1 kg stone lifted to I m on Jupiter
Given that the acceleration due to gravityon Earth, the Moon and Jupiter are l0 m s-2,
2ms-2 and25 m s-2 respectively, which ofthefollowing statements is true?
A More energy is required for case 2 thancase 1.
B More energy is required for case I than
case 3.
C Case 1 and case 2 require the same amount
of energy.
D Case I and case 3 require the same amount
ofenergy. ( )
17. Abox is being pushed horizontally on a smooth
surface by a 10 N force for 6 m. What is the
increase in the kinetic energy of the box?
A O.6J
C I6JB I.7JD 6OJ (
IVg
v
u
V,
18. A 1.2 kg box is being pushed horizontally on a
smooth surface by a l0 N force for 6 m. Giventhat the box is initially at rest, what is the speed
of the box at the end of the 6 m?
A 2ms-rC 50ms-l
B l0ms-'D 100ms-t ()
19. A 6 kg box is being pushed horizontally on asmooth surface by a l0 N force for 6 m. Giventhat the box has an initial speed of 4 m s-r, whatis the speed of the box at the end of the 6 m?
_r5;;;
A 2.0ms'C 6.0ms'
B 4.5ms'D lOmsl ()
20. A6 kg box is being pushed horizontally on asurface by a 10 N force for 6 m. Given that the
box has an initial speed of4 m s-rand the floorhas a limiting friction of 2 N, what is the speed
of the box at the end of the 6 m?
l0N6kg---------n
A 2.0 m s-t
C 5.7 m s-'
B 4.5 m s-'
D l0ms-' ()
1. A 6 kg box is being pushed horizontally on asurface by a l0 N force for 6 m. Given that the
box has an initial speed of4 m s-r and a finalspeed of 5 m s-1 at the end of the 6 m, what isthe friction between the box and the surface?
l0N6kg
A 2.ON
C 5.5NB 3.5ND 6.ON
4t Unit 7 Energy, Work and Power
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22. A box of 6 kg mass is being pulled up a
ramp by a force F at a constant speed as
shown. Given that the friction along the
surface is 4 N, what is the force F requiredto bring the box to the top of the ramp?(g=t0Nkg-')
6m 4 m
F
6kg
A4NC 44N
A 4NC 46N
6kg
AONC 12N
B 42ND 64N
)
()
B 4OND 64N
23. A box of 6 kg mass is being pulled up a
ramp by a force F from rest as shown. Given
that the friction along the surface is 4 Nand the flnal speed of the box on top of the
ramp is 2 m s r, what is the force F requiredto bring the box to the top of the ramp?(g=10Nkg')
6m
6kg
4
F
24. A box of 6 kg mass is being pulled bya 50-N force from an initial speed of4 m s-r at the foot of the ramp to a final speed
of 6 m s-r at the top of the ramp. What isthe magnitude of friction along the ramp?(g=t0Nkg-')
6m
B 4ND 5ON )
50
42
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Unit 7 Energy, Work and Power
V* Abox is being pulled by an 8-N force as shown,
from an initial speed of 4 m s lat the foot ofthe ramp to a final speed of 6 m s-r at the topof the ramp. Given that the friction along the
ramp is 2 N, what is the mass of the box?(g=t0Nkg-')
8N
M 60" t------t-
5m
B 0.6 kg
D 2.4k9
V,
N
26. A box of mass 2 kg has an initial speed of10 m s I at the foot of the ramp. Given thatthe friction along the ramp is 2 N, calculate
the maximum height h that it can reach.(g=10Nkg')
10msl
2kg 60' t
A 0.2 kg
C t.Zkg
A 2.8mC 5.0m
A 2.5mC 4.5m
B 4.5mD 43.3 m
B 3.4mD 6.0m
)
()
()
h
27 . A box of mass 2 kg has an initial speed of10 m s Iat the foot of the ramp. Given that the
friction along the ramp is 2 N, calculate the
height ft that it reaches when the speed of the
box is 5 m s-1. (8 = l0 N kg-1)
l0 m s-l
60"
I
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I
I
I
I
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r -l-l-
J
| -l-l- i
I
I
I
I
I
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I
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w,28. A box of mass 2 kg slides down from the topof the ramp with an initial speed of 0 m s-r.
Given that the friction along the ramp is 3.2 N,calculate the speed ofthe box when it reaches
the foot of the ramp. (S = l0 N/kg)
2ke
3m
m4
A 2.8 m s-'
C 8.0 m s-r
B 4.5 m s-t
D 8.9 m s-' ()
d
d
29. Abox is being pushed horizontally on a smooth
surface by a 10 N force for 6 m in 3 s. Whatis the power acting on the box during thisperiod?
lON r-----t T---------ttl
+------r-------)6m
A 5W B lSWc 20w D 600w
30. A man lifts a box of mass 2 kg verticallyupwards by 3 m. Given that he takes 6 s to do the
work, what is the power generated by the man?(g=10msa)
A lw B 6WclOw D360w ( )
31. A bullet hits a target board at a speed of300 m s 1. Given that the bullet is finallyembedded 3.0 cm into the target board and themass of the bullet is 15 g, what is the average
resistive force acting on the bullet while it ispenetrating into the target board?
A 225N B 2250Nc 22s00N D 225000N ( )
()
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32. A 100 g mass drops from a 10 m building. Whatis the kinetic energy of the mass when it is 2 maway from the floor? (g = l0 m s-2)
AOJ B2Jc 8J D lOJ ( )
33. A 100 g mass drops from a l0 m building. Whatis the speed of the mass when it is 4 m awayfrom the floor? (g = 10 m s-2)
A 4ms-t B 6ms-tC 8ms-r D llms-' ( )
U
Vru.
A 1000 kg motorcar travels at a constant speed
of 30 m s-r along a road with frictional forceof 100 N. What is the power generated by themotorcar? (8 = l0 m s-2)
A 3000w B 4500wc 300000w D 4s0000w ( )
35. A motorcar of mass 500 kg generates a powerof l0 000 W How much time does the motorcarneed to accelerate from a speed of l0 m s-r to20 m s-1?
A 2.5 s B 5.0sC7.5s D10s ( )
U
A motorcar of mass 500 kg generates a powerof 10 000 W. Given that the total resistance onthe motorcar is 200 N, how much time does
the motorcar need to accelerate from a speed of10 m s-r to 20 m s-1?
A 6.3s B 8.3sC 9.2s D 10.7s ( )
37. A 100 W spotlight has an efficiency of 40Vo.
How much light energy can the spotlightproduce in an hour?
A t44kJ B 216kJc 360kJ D '720kJ ( )
43 Unit 7 Energy, Work and power
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38. A worm of mass 2 g crawls up a flight of steps
from point A to point B as shown. What is the
work done by the worm? (g = l0 N kg ')
2cm t 3cm
2cm t 3cm
^ I Cf{l t ---+3cm
<---'3cm
A 1.2 mJ
c 0.12t
B
A
39. A worm of mass 2 g crawls up a flight ofsteps from point A to point B as shown. Given
that the friction of the floor on the worm is
0.001 N, what is the work done by the worm?
2cm r 3cm
2cm t 3cm
^AI CITI r ---+3cm
<---)3cm
A 0.12 mJ
C 1.20 mJ
B 3.6 mJ
D I2OJ
B 0.18 mJ
D 1.38 mJ
()
()
B
A
The speed-time graph below shows the motion
of a motorcar on a level road within a l0 s
duration. Given that the mass of the motorcar
is 500 kg and the frictional force along the road
is 120 N, what is the power of the motorcar?
v/ms'
t2
4
tls
A 3200Wc 32000w
10
B 4160WD 41 600W
0
(
Vo,
Extension Questions
A mass of 2 kg is suspended by a 1.0 m longstring and is set free at point A as shown.Neglecting air resistance, what is the speed ofthe mass as it passes through point B?(8=10ms-2)
i
--*
l'---
I ,,'-l5--
B
A l.5ms-tC 3.2 m s-'
B 2.3 m s-t
D 4.1 m s-l (
U
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Uoo
42. A box of mass 3 kg is being pulled along a
horizontal bench at a constant speed of 5 m s-'
by a l0-N horizontal force. What is the workdone against friction in 4 s?
A OJ B 2OOT
c 600J D 1000J ( )
A block of mass rn slides from rest down a
smooth incline of length L. As a result, it moves
through a vertical height y, and a horizontaldistance x. When it reaches the bottom of the
incline, what is its kinetic energy?(Take acceleration due to gravity as g)
A mgL B *gyC (O.S)mx'z D (0.5)my2 ( )
Acar of mass lrt has an engine which can deliverpower P. What is the minimum time in which
the car can be accelerated from rest to a speed
v?
Amv
P
mv'
P
mv
2P,mv
B
D (
44
C2P
Unit 7 Energy, Work and Power
)
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1kg
A
A block of mass I kg has a speed of 20 m s-r at
point A. It is moving towards point C. Giventhat the frictional force along AB is 10 N and
the frictional force along BC is 5 N, what is thespeed of the block when it reaches point C andwhat is the time taken for the process? (Take
acceleration due to gravity to be l0 m s-2)
Height3m
3m 4m
C
Speed
A 15.2 m s-'
B 15.2 m s-'
C 17.0 m s-'
D 17.0 m s-'
Time taken
0.45 s
0.55 s
0.65 s
0.75 s ()
Vou. A bullet leaves the vertical barrel of a rifle and
reaches aheightof 720 m. What is the speed ofthe bullet when it leaves the barrel of the rifle toachieve this height? (Given that the acceleration
due to gravity is 10 m s-2)
A l20ms' B 170ms-1C 240ms-t D l4z00ms' ( )
N/U47. A cable car of mass 200 kg travels up a hill from
an altitude of 1030 m to an altitude of ll50 m.During this period, the cable car moves througha total of 250 m cable length in 5 min. What isthe rate ofincrease ofpotential energy?
A 800w B 1000wc 39500w D 48000w ( )
Wor.
Wo,
A block made from steel falls from position 1
to position 2 as shown. How much potentialenergy is lost during the process? (g = l0 m s-2,
density of steel = 8000 kg m')2m
2m
l0m
Position I
A I2.8 MJC 25.6MJ
A 0.5 m s-t
C l.7ms-t
Position 2
B 16.0 MJD 32.0 MJ
B l.l ms-rD 2.5 m s-l
(
A block resting on a smooth horizontal floor isbeing pushed by a constant horizontal force.
Find the following ratio:
Kinetic Kinetic Kineticenergy energy energy
gained in gained in gained inl" second 2nd second 3'd second
B l:4:9D l:1:1
A l:2:3C l:3:5 )
NVt)SO. e I kg mass and a 5 kg mass are held at a
position across a ramp as shown. Given thatthe friction along the ramp is 10 N, what isthe speed of the I kg mass after the masses
are released and the 1 kg mass has moved for10 cm?
5kg
lkgI
t l0cmi
()
45 Unit 7 Energy, Work and Power
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