Choose
the best answer to each question and write the appropriate letter in the
space below.
1) In physics, work is defined as __________.
A) force times time.
B) force divided by time.
C) force times distance.
D) force divided by distance.
E) distance divided by time. ________
2) If you lift two loads up one story, how much work do you do compared
to lifting just one load up one story?
A) Four times as much
B) Twice as much
C) The same amount
D) One half as much
E) One quarter as much ________
3) If you lift one load up two stories, how much work do you do compared
to lifting one load up only one story?
A) Four times as much
B) Twice as much
C) The same amount
D) One half as much
E) One quarter as much ________
4) If Nellie Newton pushes an object with twice the force for twice the
distance, she does __________.
A) the same work.
B) twice the work.
C) four times the work.
D) eight times the work. ________
5) The unit of work is the __________.
A) newton.
B) watt.
C) meter.
D) joule.
E) second. ________
6) Power is defined as the __________.
A) force on an object times the distance the object moves.
B) force on an object divided by the time the force acts.
C) work done on an object divided by the time taken to do the work.
D) work done times the time taken to do that work.
E) distance divided by the time taken to move that distance. ________
7) The unit of power is the __________.
A) newton.
B) watt.
C) meter.
D) joule.
E) second. ________
8) Potential energy is the energy an object has because of its __________.
A) speed.
B) location.
C) size.
D) temperature.
E) density. ________
9) The amount of potential energy possessed by an elevated object is equal
to __________.
A) the force needed to lift it.
B) the distance it is lifted.
C) the power used to lift it.
D) the work done in lifting it.
E) the value of the acceleration due to gravity. ________
10) Kinetic energy of an object is equal to __________.
A) one half the product of its mass times its speed squared.
B) one half the product of its mass times its speed.
C) its mass multiplied by its speed.
D) its mass multiplied by its acceleration.
E) its mass multiplied by its acceleration squared. _______
11) How much farther will a car traveling at 100 km/s skid than the same
car traveling at 50 km/s?
A) Five times as far
B) Four times as far
C) Twice as far
D) The same distance
E) Half as far _______
12) An arrow in a bow has 70 J of potential energy. Assuming no loss of
energy due to heat, how much kinetic energy will it have after it has
been shot?
A) 140 J
B) 70 J
C) 50 J
D) 35 J
E) 0 J _______
13) Energy is changed from one form to another with no net loss or gain.
A) Always true
B) Sometimes true
C) Always false _______
14) As a pendulum swings back and forth __________.
A) potential energy is transformed into kinetic energy.
B) kinetic energy is transformed into potential energy.
C) at the lowest part of its swing, its energy is all kinetic.
D) at the end points of its swing, its energy is all potential.
E) all of the above _______
15) An object that has linear kinetic energy must be __________.
A) moving.
B) at an elevated position.
C) at rest.
D) none of the above _______
16) Cannonballs are launched from an airplane in the forward direction
of motion. The momentum of the airplane will be __________.
A) decreased.
B) unchanged.
C) increased. _______
17) A woman can lift barrels a vertical distance of 1 meter or can roll
them up a 2 meterlong ramp to the same elevation. If she uses the ramp,
the applied force required is __________.
A) one quarter as much.
B) half as much.
C) twice as much.
D) four times as much.
E) the same amount. _______
18) A job is done slowly, and an identical job is done quickly. Both jobs
require the same amount of work but different amounts of __________.
A) energy.
B) power.
C) both A and B
D) none of the above _______
19) Which requires more work: lifting a 50kg sack vertically 2 meters
or lifting a 25kg sack vertically 4 meters?
A) Lifting the 50kg sack
B) Lifting the 25kg sack
C) Both require the same amount of work. _______
20) A ball is thrown into the air with 100 J of kinetic energy, which
is transformed to gravitational potential energy at the top of its trajectory.
When it returns to its original level after encountering air resistance,
its kinetic energy is __________.
A) less than 100 J.
B) more than 100 J.
C) 100 J.
D) Not enough information given. _______
21) An object that has kinetic energy must be __________.
A) moving.
B) falling.
C) elevated.
D) at rest. _______
22) An object that has kinetic energy must have __________.
A) momentum.
B) acceleration.
C) a force applied to maintain it.
D) none of the above _______
23) Which has greater kinetic energy, a car traveling at 30 km/h or a
halfasmassive car traveling at 60 km/h?
A) The 30km/h car
B) The 60km/h car
C) Both have the same kinetic energy. _______
24) A person on a roof throws one ball downward and an identical ball
upward at the same speed. The ball thrown downward hits the ground with
100 J of kinetic energy. Ignoring air friction, with how much kinetic
energy does the second ball hit the ground?
A) 100 J
B) 200 J
C) Less than 100 J
D) More than 200 J
E) none of the above _______
25) An object at rest may have __________.
A) speed.
B) velocity.
C) energy.
D) momentum.
E) none of the above _______
26) A heavy object and a light object are released from rest at the same
height and time in a vacuum. As they fall, they have equal __________.
A) weights.
B) momenta.
C) energies.
D) all of the above
E) none of the above _______
27) If an object has kinetic energy, then it also must have __________.
A) impulse.
B) momentum.
C) acceleration.
D) force.
E) none of the above _______
28) If the velocity of a moving object doubles, then what else doubles?
A) momentum.
B) kinetic energy.
C) acceleration.
D) all of the above
E) none of the above _______
29) All simple machines ideally work on the principle that __________.
A) impulse equals momentum change.
B) force equals mass times acceleration.
C) kinetic energy transforms into potential energy.
D) total momentum before a collision equals total momentum after the collision.
E) work input equals work output. _______
30) The ratio of output force to input force of a simple machine is called
the __________.
A) fulcrum.
B) pivot point.
C) efficiency.
D) mechanical advantage.
E) lever arm. _______
31) A pulley system can __________.
A) change the direction of a force.
B) multiply the force.
C) increase the amount of work done.
D) Both A and B
E) Both B and C _______
32) The ratio of useful work output to total work input is called the
__________.
A) fulcrum.
B) pivot point.
C) efficiency.
D) mechanical advantage.
E) lever arm. _______
33) About how efficient is a typical gasolineburning car engine?
A) 100%
B) 70%
C) 30%
D) 5% _______
34) A small economy car (low mass) and a limousine (high mass) are pushed
from rest across a parking lot, equal distances with equal forces. The
car that receives more change in kinetic energy is the __________.
A) small economy car.
B) limousine.
C) same for each. _______
35) A popular swinging apparatus consists of an aligned row of identical
elastic balls suspended by strings so they touch each other. When two
balls on one end are elevated and released, they slam into the array of
balls and two balls pop out the other side. If instead, one ball popped
out with twice the speed, this would be a violation of the conservation
of __________.
A) momentum.
B) energy.
C) both. _______
36) Consider molecules of hydrogen gas and molecules of heavier oxygen
gas that have the same kinetic energy. The molecules with more speed are
__________.
A) hydrogen.
B) oxygen.
C) Both have the same speed. _______
37) How many joules of work are done on an object when a force of 10 N
pushes it 5 m?
A) 50 J
B) 10 J
C) 5 J
D) 2 J
E) 1 J _______
38) How much power is required to do 100 J of work on an object in 2 seconds?
A) 200 W
B) 100 W
C) 50 W
D) 2 W
E) 0 W _______
39) How much work is done on a 50N rock that you carry horizontally across
a 10m room?
A) 500 J
B) 50 J
C) 10 J
D) 5 J
E) 0 J _______
40) How much work is done on a 50N rock that you lift 10 m?
A) 500 J
B) 50 J
C) 10 J
D) 1 J
E) 0 J _______
41) How much power is expended if you lift a 50N rock 10 meters in 1
second?
A) 500 W
B) 50 W
C) 10 W
D) 5 W
E) 0 W _______
42) Suppose a moving car has 2000 J of kinetic energy. If the car's speed
doubles, how much kinetic energy would it then have?
A) 8000 J
B) 6000 J
C) 4000 J
D) 2000 J
E) 1000 J _______
43) It takes 40 J to push a large box 4 m across a floor. Assuming the
push is in the same direction as the move, what is the magnitude of the
force on the box?
A) 4 N
B) 10 N
C) 40 N
D) 160 N
E) none of the above _______
44) If Kelly the skater's speed increases so he has twice the momentum,
then his kinetic energy increases by __________.
A) two times.
B) four times.
C) eight times.
D) none of the above (KE remains the same.) _______
45) A 10N object moves at 1 m/s. Its kinetic energy is __________.
A) 0.5 J.
B) 1 J.
C) 10 J.
D) more than 10 J. _______
46) A girl can easily lift an 80N rock with the help of a lever. When
she pushes down with 10 N of force, she lifts the rock 0.1 meters. How
far does she move her arms to do this?
A) 10 m
B) 8 m
C) 1 m
D) 0.8 m
E) 0.1 m _______
47) A pulley has two supporting strands. In order to use it to lift a
load 1 meter, the person pulling will have to pull a distance of __________.
A) 4 m.
B) 2 m.
C) 1 m.
D) 1/2 m.
E) 1/4 m. _______
48) A frictionless inclined plane is 6 m long and rests on a wall that
is 2 m high. How much force is needed to push a block of ice weighing
300 N up the plane?
A) 600 N
B) 300 N
C) 200 N
D) 100 N
E) 50 N _______
49) A certain jack has a theoretical mechanical advantage of 500. However,
due to frictional forces, the actual mechanical advantage is only 100.
What is the efficiency of the jack?
A) 50 000
B) 500
C) 50
D) 5
E) 1/5 _______
50) A machine puts out 100 watts of power for every 1000 watts put into
it. The efficiency of the machine is __________.
A) 10%.
B) 50%.
C) 90%.
D) 110%.
E) none of the above _______
Write True or False in the space provided.
51) In physics, the amount of work done on an object is the product of
the force exerted on the object times the time the object moves. _______
52) The unit of work is called the joule. _______
53) The rate at which work is done is called energy. _______
54) The unit of power is the watt. _______
55) The rate at which work is done is called power. _______
56) The energy an object has by virtue of its location is its potential
energy. _______
57) The energy an object has by virtue of its motion is its kinetic energy.
_______
58) The ratio of output force to input force for a simple machine is its
efficiency. _______
59) The ratio of useful work output to total work input is mechanical
advantage. _______
60) When we carry an object across a room, without lifting it or setting
it down, we do no physical work on it. _______
61) More power is needed to carry a heavy suitcase slowly up a flight
of stairs than to carry the suitcase quickly up the same flight of stairs.
_______
62) Energy transforms from one form to another with no net loss or gain.
_______
63) A pulley system can only change direction; it can't multiply forces
as well. _______
64) Using an inclined plane is an effective way to lift a heavy object
that you otherwise couldn't lift. _______
On a separate sheet of paper, answer the following questions.
65) You do work on something when you lift it against gravity. How does
this work relate to gravitational potential energy? If the lifted object
is released, what becomes of this energy? Be sure to define all terms
that you use.
66) Discuss how energy conservation applies to a pendulum. Where is potential
energy the most? The least? Where is kinetic energy the most? The least?
Where is the pendulum accelerating the most? The least? Where is it moving
the fastest? Stopped?
67) Define a simple machine and give examples of four different ones.
For each machine discuss the theoretical mechanical advantage, actual
mechanical advantage, and efficiency and give numerical examples of each.
Answer the following questions in the space provided. Show all work.
68) What is the work done in lifting 50kg of bricks to a height of 20
m?
_____________
69) What is the work done in raising a 50kg block 3.0 m vertically ?
_____________
70) What amount of work is done on a cart that is pushed 4.0 m across
a floor by a horizontal 50N net force?
_____________
71) If possible, determine the power expended when a barbell is raised
5.0 m in 2 s.
_____________
72) A toy cart moves with a kinetic energy of 30 J. If its speed is doubled,
what will its kinetic energy be?
_____________
73) In raising a 3,000N piano with a pulley system, it is noted that
for every 1 m of rope pulled down, the piano rises 0.1 m. Ideally, what
force is needed to lift the piano?
_____________
74) A car traveling at 50 km/h will skid 20 m when its brakes are locked.
If the same car is traveling at 150 km/h, what will be its skidding distance?
_____________
75) What amount of work can a 600W electric drill do in 4 minutes?
_____________
76) A couch potato might consume 6 million J of energy in a day. What
is this rate of energy consumption in watts?
_____________
77) A 40kg boy runs up the staircase to a floor 5.0 m higher in 7.0 seconds.
What is his power output?
_____________
78) At what height does a 1,000.0kg mass have a potential energy of 1.0
J relative to the ground?
_____________
79) The 2.0kg head of an ax is moving at 5.0 m/s when it strikes a log
and penetrates 0.02 m into the log. What is the average force the blade
exerts on the log?
_____________
80) An anvil hanging vertically from a long rope in a barn is pulled to
the side and raised like a pendulum 0.80 m above its equilibrium position.
It then swings to its lowermost point where the rope is cut by a sharp
blade. The anvil then has a horizontal velocity with which it sails across
the barn and hits the floor, 5.0 m below. How far horizontally along the
floor will the anvil land?
_____________
