QUIZ QUIZ Who wants to be a Who wants to be a

“future” millionaire??“future” millionaire??

QUIZ QUIZ Who wants to be a Who wants to be a

“future” millionaire??“future” millionaire??

Learning physics is not too bad Learning physics is not too bad although you are already although you are already

sickened.sickened.

Question 1• A mass of 400 grams is

accelerated at 30 cm/s2. The force, in N, to accelerate this mass is…

The answer to Q1• 0.12 newtons

F = ma = 0.4 kg 0.3m/s2

Question 2• A walker walks 30 m from the

origin toward the WEST to point A. She then walks from point A, 20 m more toward the EAST to point B. What is the walker’s total displacement from the origin?

Answer to Q210 m toward the WEST (or -10 m)

Distance and displacement are different!!

Question 3• A force of 56 N is directed 35

degrees NORTH of EAST. What is the EAST component of the force?

Answer to Q345.9 N

Do you remember when to use cos or sin for this type of problem?

Question 4• A momentum change is found as

5.8 kg m/s with the time interval, 0.22 s. What is the force acting on it during the time?

Answer to Q426 N

The change in momentum is equal to the impulse, Fs.

Question 5• What is the Kepler’s third law?(a) The gravity is always the same with

the equal period of the orbit.(b) The square of the orbit period of a

planet is proportional to the cube of the semi-major axis of its orbit.

(c) A line segment joining a planet and the Sun sweeps out equal areas during equal intervals of time.

Answer to Q5(b)

The formula is (T1/T2)2=(r1/r2)3

Question 6• What is the meaning of the

specific heat?

Answer to Q6Specific heats depend on materials.

The more specific heat it has, the harder to raise (or lower) the temperature with a certain heat.

Question 7• What are conservative and

nonconservative forces?

Answer to Q7A conservative force is derived from the

correspondent potential energy, such as gravitational potential energy.

A nonconservative force is not derived from the potential energy and its work depends on the path taken, such as frictional force, normal force, etc.

Question 8• A ball is projected from the origin

with a velocity of 20.0 m/s at an angle of 60 degrees above the horizontal. What is the maximum height of the ball?

Answer to Q815.3 m

First, obtain the y-component of the velocity. Then, use v2=v0

2-2gy, which is your favorite.

Question 9• A 4,000 kg satellite is traveling in a

circular orbit 200 km above the surface of the earth. A 3.0 gram marble is dropped inside the satellite. What is the force of gravity on the marble as viewed by the observers on the earth? (Me = 5.98 x 1024 kg, Re = 6.37 x 106 m, G = 6.67 x 10-11 Nm2 /kg2)

Answer to Q90.0277 N

Use F=GmM/r2 including the radius of the Earth. However, do not use the mass of the satellite.

Question 10• As for gravitational acceleration, 9.8

m/s2, which one of the following is true?a) Gravitational accel. is greater when an

object is thrown up.b) Gravitational accel. is smaller when an

object falls downward.c) Gravitational accel. is always the same

wherever the object is placed on the Earth.

Answer to Q10c) is the correct statement.

9.8 m/s2 is always the same (close to the surface) and directed to the center of the Earth.

Question 11• What is the law of conservation of

mechanical energy?

Answer to Q11The total mechanical energy in a

system remains constant as long as the only forces acting are conservative forces.

Question 12• A 3.0-kg object is placed on

horizontal and rough surface. If the coefficient of static friction is 0.20, what is the force to move the object?

Answer to Q125.88 N

The frictional force is the normal force the coefficient of friction.

The normal force in this case is mg.

Question 13• What is Newton’s Law of Universal

Gravitation? Choose one related equation.

a) W = mgb) F=GmM/r2

c) F=mv2/rd) F=mae) V=2r/T

Answer to Q13b) is the correct equation.

The law to describe the force between masses is Newton’s Law of Universal Gravitation.

Question 14• Here is an equation: ΔQ/ΔT = e σ A (T1

4 - T24) .

What are e and σ called? Which situation can you use this equation?

Answer to Q14e is emissivity.σ is Stefan-Boltzmann constant,

5.670373 × 10-8 kg s-3 K-4.

This equation is used for radiation of heat.

Question 15• What is the apparent weight?a) It is always that the mass of the

object times gravity.b) It is equal to weightlessness.c) It is the net mass of the object.d) It is the net weight you can feel

how heavy it is.

Answer to Q15d) is the correct description of

apparent weight.

In this sense, the apparent weight can be zero (weightlessness ) due to an inertial force.

Question 16• What is the work-(kinetic) energy

theorem? Choose one of the best equation to describe it.

a) KEf-KEi=W

b) KEf=KEi

c) fk=kn

d) pf-pi=Fs

e) Qgained=Qlost

Answer to Q16a) is the correct expression to

describe the work-(kinetic) energy theorem.

You should be able to explain it in your own words.

Question 17• Find the impulse from the graph.

F (N)

t (s)0.02 0.04 0.06 0.08 0.10 0.12

20

40

60

Answer to Q170.9 Ns

You can find the area, 60 N (0.09 – 0.06) s ½. (The area of the triangle)

Question 18• What is the following equation

mean? Q/t=kA(T1-T2)/

What is a condition that the equation can be valid?

Answer to Q18• That is used for conduction of heat.

Q/t represents the rate of the heat transfer. The k is conductivity, A is area, is the length to conduct, etc.

• The equation assumes that the heat does not go away from the side of the object (conducting only one way).

Are you ready for the final?

• Ask yourself why you have to use the specific equation to solve the problem.

• There are always concepts behind physics problems, so don’t pick up numbers and plug in equations you randomly find from the equation sheet!!

• Make sure the definition of each physics term.