Deck 6: Work and Energy

Question 1

Choose the one alternative that best completes the statement or answers the question.
When you throw a pebble straight up with initial speed V, it reaches a maximum height H with no air resistance. At what speed should you throw it up vertically so it will go twice as high?

A) 2 V
B) 8 V
C) $\sqrt { 2 } V$
D) 4 V
E) 16 V

Answer 1

C

Question 2

Choose the one alternative that best completes the statement or answers the question.
Which one has larger kinetic energy: a 500-kg object moving at 40 m/s or a 1000-kg object moving at 20 m/s?

A) The 500-kg object
B) The 1000-kg object
C) Both have the same kinetic energy.

Answer 2

The 500-kg object

Question 3

Choose the one alternative that best completes the statement or answers the question.
A truck has four times the mass of a car and is moving with twice the speed of the car. If $K _ { \mathrm { t } } \text { and } K _ { \mathrm { c } }$ refer to the kinetic energies of truck and car respectively, it is correct to say that

A) $K _ { \mathrm { t } } = 16 K _ { \mathrm { C } }$
B) $K _ { \mathrm { t } } = 2 K _ { \mathrm { C } }$
C) $K _ { \mathrm { t } } = K _ { \mathrm { C } }$
D) $K _ { \mathrm { t } } = \frac { 1 } { 2 } K \mathrm { c }$
E) $K _ { \mathrm { t } } = 4 K _ { \mathrm { C } }$

Answer 3

A

Question 4

Choose the one alternative that best completes the statement or answers the question.
Which requires more work, increasing a car's speed from 0 mph to 30 mph or from 50 mph to 60 mph?

A) 50 mph to 60 mph
B) 0 mph to 30 mph
C) It is the same in both cases.

Question 5

Choose the one alternative that best completes the statement or answers the question.
Two men, Joel and Jerry, push against a car that has stalled, trying unsuccessfully to get it moving. Jerry stops after 10 min, while Joel is able to push for 5.0 min longer. Compare the work they do on
The car.

A) Joel does 25 % more work than Jerry.
B) Jerry does 50 % more work than Joel.
C) Joel does 50 % more work than Jerry.
D) Joel does 75 % more work than Jerry.
E) Neither of them does any work.

Question 6

Choose the one alternative that best completes the statement or answers the question.
Three cars (car L, car M, and car N) are moving with the same speed and slam on their brakes. The most massive car is car L, and the least massive is car N. If the tires of all three cars have identical
Coefficients of kinetic friction with the road surface, for which car is the amount of work done by
Friction in stopping it the greatest?

A) The amount of work done by friction is the same for all cars.
B) Car N
C) Car M
D) Car L

Question 7

Choose the one alternative that best completes the statement or answers the question.
The graphs shown show the magnitude F of the force exerted by a spring as a function of the distance x the spring has been stretched. For which one of the graphs does the spring obey Hooke's Law?
a)

b)

c)

d)

e)

A) Graph a
B) Graph b
C) Graph c
D) Graph d
E) Graph e

Question 8

Choose the one alternative that best completes the statement or answers the question.
If the force on an object is in the negative direction, the work it does on the object must be

A) negative.
B) positive.
C) The work could be either positive or negative, depending on the direction the object moves.

Question 9

Choose the one alternative that best completes the statement or answers the question.
You slam on the brakes of your car in a panic, and skid a certain distance on a straight level road. If you had been traveling twice as fast, what distance would the car have skidded, under the same
Conditions?

A) It would have skidded 4 times farther.
B) It would have skidded one half as far.
C) It would have skidded 1.4 times farther.
D) It would have skidded twice as far.
E) It is impossible to tell from the information given.

Question 10

Choose the one alternative that best completes the statement or answers the question.
When you drop a pebble from height H, it reaches the ground with kinetic energy K if there is no air resistance. From what height should you drop it so it will reach the ground with twice as much
Kinetic energy?

A) 4H
B) 8H
C) $\sqrt { 2 H }$
D) 16H
E) 2H

Question 11

Choose the one alternative that best completes the statement or answers the question.
A stone is held at a height h above the ground. A second stone with four times the mass of the first one is held at the same height. The gravitational potential energy of the second stone compared to
That of the first stone is

A) four times as much.
B) one-fourth as much.
C) one-half as much.
D) twice as much.
E) the same.

Question 12

Choose the one alternative that best completes the statement or answers the question.
A 4.0 kg object is moving with speed 2.0 m/s. A 1.0 kg object is moving with speed 4.0 m/s. Both objects encounter the same constant braking force, and are brought to rest. Which object travels
The greater distance before stopping?

A) the 1.0 kg object
B) the 4.0 kg object
C) Both objects travel the same distance.
D) It cannot be determined from the information given.

Question 13

Choose the one alternative that best completes the statement or answers the question.
You throw a baseball straight up. Compare the sign of the work done by gravity while the ball goes up with the sign of the work done by gravity while it goes down.

A) The work is positive on the way up and positive on the way down.
B) The work is negative on the way up and positive on the way down.
C) The work is positive on the way up and negative on the way down.
D) The work is negative on the way up and on the way down because gravity is always downward.

Question 14

Choose the one alternative that best completes the statement or answers the question.
A 35-N bucket of water is lifted vertically 3.0 m and then returned to its original position. How much work did gravity do on the bucket during this process?

A) 0 J
B) 180 J
C) 45 J
D) 90 J
E) 900 J

Question 15

Choose the one alternative that best completes the statement or answers the question.
A heavy dart and a light dart are launched horizontally on a frictionless table by identical ideal springs. Both springs were initially compressed by the same amount. Which of the following
Statements about these darts are correct? (There could be more than one correct choice.)

A) Both darts had the same initial elastic potential energy.
B) The lighter dart leaves the spring moving faster than the heavy dart.
C) The darts both have the same kinetic energy just as they move free of the spring.
D) The heavy dart had more initial elastic potential energy than the light dart.
E) Both darts move free of the spring with the same speed.

Question 16

Choose the one alternative that best completes the statement or answers the question.
You and your friend, who weighs the same as you, want to go to the top of the Eiffel Tower. Your friend takes the elevator straight up. You decide to walk up the spiral stairway, taking longer to do
So) Compare the gravitational potential energy of you and your friend, after you both reach the
Top)

A) Your friend's gravitational potential energy is greater than yours, because he got to the top faster.
B) It is impossible to tell, since the times you both took are unknown.
C) It is impossible to tell, since the distances you both traveled are unknown.
D) Your gravitational potential energy is greater than that of your friend, because you traveled a greater distance in getting to the top.
E) Both of you have the same amount of gravitational potential energy at the top.

Question 17

Choose the one alternative that best completes the statement or answers the question.
Two objects, one of mass m and the other of mas $2 m$ are dropped from the top of a building. If there is no air resistance, when they hit the ground

A) the heavier one will have half the kinetic energy of the lighter one.
B) both will have the same kinetic energy.
C) the heavier one will have twice the kinetic energy of the lighter one.
D) the heavier one will have one-fourth the kinetic energy of the lighter one.
E) the heavier one will have four times the kinetic energy of the lighter one.

Question 18

Choose the one alternative that best completes the statement or answers the question.
Person X pushes twice as hard against a stationary brick wall as person Y. Which one of the following statements is correct?

A) Both do the same amount of positive work.
B) Both do positive work, but person X does one-half the work of person Y.
C) Both do positive work, but person X does four times the work of person Y.
D) Both do positive work, but person X does twice the work of person Y.
E) Both do zero work.

Question 19

Choose the one alternative that best completes the statement or answers the question.
Three cars (car F, car G, and car H) are moving with the same speed and slam on their brakes. The most massive car is car F , and the least massive is car H. If the tires of all three cars have identical coefficients of kinetic friciton with the road surface, which car travels the longest distance to skid to a stop?

A) They all travel the same distance in stopping.
B) Car G
C) Car F
D) Car H

Question 20

Choose the one alternative that best completes the statement or answers the question.
When you drop a pebble from height H, it reaches the ground with speed V if there is no air resistance. From what height should you drop it so it will reach the ground with twice speed?

A) 2H
B) 8H
C) 5H
D) 16H
E) 4H

Question 21

Choose the one alternative that best completes the statement or answers the question.
A heavy sled and a light sled, both moving horizontally with the same kinetic energy, suddenly slide onto a rough patch of snow and eventually come to a stop. The coefficient of kinetic friction
Between the sleds and the rough snow is the same for both of them. Which of the following
Statements about these sleds are correct? (There could be more than one correct choice.)

A) The light sled will slide farther on the rough snow than the heavy sled.
B) Both sleds will slide the same distance on the rough snow before stopping.
C) On the rough snow, the change in kinetic energy will be the same for both sleds.
D) The heavy sled will slide farther on the rough snow than the light sled.
E) The friction from the snow will do the same amount of work on both sleds.

Question 22

Choose the one alternative that best completes the statement or answers the question.
A 1-kg ball is released from a height of 6 m, and a 2-kg ball is released from a height of 3 m. Air resistance is negligible as they fall. Which of the following statements about these balls are correct?
(There could be more than one correct choice.)

A) As they reach the ground, the 1-kg ball will have more kinetic energy than the 2-kg ball because it was dropped from a greater height.
B) Both balls will reach the ground with the same kinetic energy.
C) Both balls will reach the ground with the same speed.
D) Both balls will take the same time to reach the ground.
E) As they reach the ground, the 1-kg ball will be moving faster than the 2-kg ball.

Question 23

Choose the one alternative that best completes the statement or answers the question.
A force produces power P by doing work W in a time T . What power will be produced by a force that does six times as much work in half as much time?

A) 12P
B) 6P
C) P
D) $\frac { 1 } { 12 } P$
E) $\frac { 1 } { 6 } P$

Question 24

Choose the one alternative that best completes the statement or answers the question.
A heavy rock and a light rock are dropped from the same height and experience no significant air resistance as they fall. Which of the following statements about these rocks are correct? (There
Could be more than one correct choice.)

A) Just as they were released, both rocks had the same amount of gravitational potential energy.
B) When they reach the ground, the heavier rock has more kinetic energy than the lighter rock.
C) Both rocks have the same kinetic energy when they reach the ground.
D) The heavier rock reaches the ground before the lighter rock.
E) Both rocks have the same speed when they reach the ground.

Question 25

Choose the one alternative that best completes the statement or answers the question.
Two identical grasshoppers jump into the air with the same initial speed and experience no air resistance. Grasshopper A goes straight up, but grasshopper B goes up at a 66° angle above the
Horizontal. Which of the following statements about these grasshoppers are correct? (There could
Be more than one correct choice.)

A) At their highest point, both of them have the same amount of gravitational potential energy.
B) At their highest point, both of them have the same amount of mechanical energy.
C) At their highest point, grasshopper A has more gravitational potential energy than grasshopper B.
D) At their highest point, both of them have the same amount of kinetic energy.
E) At their highest point, grasshopper B is moving faster than grasshopper A.

Question 26

Choose the one alternative that best completes the statement or answers the question.
Swimmers at a water park have a choice of two frictionless water slides, as shown in the figure. Although both slides drop over the same height h , slide 1 is straight while slide 2 is curved, dropping quickly at first and then leveling out. How does the speed of a swimmer reaching the bottom of slide 1 compare with $\text { v2, }$ the speed of a swimmer reaching the end of slide 2 ?

A) $v 1 < v 2$
B) $v _ { 1 } = v _ { 2 }$
C) $v _ { 1 } > v _ { 2 }$
D) The heavier swimmer will have a greater speed than the lighter swimmer, no matter which slide he uses.
E) No simple relationship exists between $v 1 \text { and } v 2$

Question 27

Choose the one alternative that best completes the statement or answers the question.
A lightweight object and a very heavy object are sliding with equal speeds along a level frictionless surface. They both slide up the same frictionless hill with no air resistance. Which object rises to a
Greater height?

A) They both slide to exactly the same height.
B) The heavy object, because it has more mass to carry it up the hill.
C) The lightweight object, because the force of gravity on it is less.
D) The light object, because gravity slows it down less.
E) The heavy object, because it has greater initial kinetic energy.

Question 28

Choose the one alternative that best completes the statement or answers the question.
Two cyclists who weigh the same and have identical bicycles ride up the same mountain, both starting at the same time. Joe rides straight up the mountain, and Bob rides up the longer road that
Has a lower grade. Joe gets to the top before Bob. Ignoring friction and wind resistance, which one
Of the following statements is true?

A) The amount of work done by Joe is greater than the amount of work done by Bob, and the average power exerted by Joe is greater than that of Bob.
B) The average power exerted by Bob and Joe was the same, but Joe exerted more work in getting there.
C) Bob and Joe exerted the same amount of work, and the average power of each cyclist was also the same.
D) The amount of work done by Joe is equal to the amount of work done by Bob, but the average power exerted by Joe is greater than that of Bob.

Question 29

Choose the one alternative that best completes the statement or answers the question.
If the units of your answer are kg · $\mathrm { m } ^ { 2 } / \mathrm { s } ^ { 3 }$ which of the following types of quantities could your answer be? (There could be more than one correct choice.)

A) kinetic energy
B) force
C) potential energy
D) work
E) power

Question 30

Choose the one alternative that best completes the statement or answers the question.
A heavy frog and a light frog jump straight up into the air. They push off in such away that they both have the same kinetic energy just as they leave the ground. Air resistance is negligible. Which
Of the following statements about these frogs are correct? (There could be more than one correct
Choice.)

A) The heavier frog goes higher than the lighter frog.
B) The lighter frog goes higher than the heavier frog.
C) They both leave the ground with the same speed.
D) Just as they leave the ground, the heavier frog is moving faster than the lighter frog.
E) Just as they leave the ground, the lighter frog is moving faster than the heavier frog.
F) Both frogs reach the same maximum height.

Question 31

Choose the one alternative that best completes the statement or answers the question.
Joe and Bill throw identical balls vertically upward. Joe throws his ball with an initial speed twice as high as Bill. If there is no air resistance, the maximum height of Joe's ball will be

A) two times that of Bill's ball.
B) roughly 1.4 times that of Bill's ball.
C) eight times that of Bill's ball.
D) four times that of Bill's ball.
E) equal to that of Bill's ball.

Question 32

Choose the one alternative that best completes the statement or answers the question.
Two frisky otters slide down frictionless hillsides of the same height but different slopes. The slope of the hill of otter 1 is $30 ^ { \circ }$ while the slope of the hill of otter 2 is $60 ^ { \circ }$ If both start from rest, which otter is moving faster when she reaches the bottom of her hill?

A) Otter 1 is moving faster.
B) Otter 2 is moving faster.
C) The heavier otter is moving faster, no matter which hill she used.
D) The otter that took the shorter time is moving faster.
E) Both otters have the same speed at the bottom.

Question 33

Choose the one alternative that best completes the statement or answers the question.
A heavy stone and a light stone are released from rest in such away that they both have the same amount of gravitational potential energy just as they are released. Air resistance is negligibly small.
Which of the following statements about these stones are correct? (There could be more than one
Correct choice.)

A) Just as it reaches the ground, the light stone is traveling faster than the heavy stone.
B) The stones both have the same kinetic energy just as they reach the ground.
C) The stones must have been released from the same height.
D) The stones both have the same speed just as they reach the ground.
E) The initial height of the light stone is greater than the initial height of the heavy stone.

Question 34

Choose the one alternative that best completes the statement or answers the question.
If a stone is dropped with an initial gravitational potential energy of 100 J but reaches the ground
with a kinetic energy of only 75 J, this is a violation of the principle of conservation of energy.

Question 35

Choose the one alternative that best completes the statement or answers the question.
Jill does twice as much work as Jack does and in half the time. Jill's power output is

A) the same as Jack's power output.
B) four times Jack's power output.
C) twice Jack's power output.
D) one-half as much as Jack's power output.
E) one-fourth as much as Jack's power output.

Question 36

Choose the one alternative that best completes the statement or answers the question.
A stone can slide down one of four different frictionless ramps, as shown in the figure. For which ramp will the speed of the ball be the greatest at the bottom?

A) Ramp X
B) Ramp Y
C) Ramp Z
D) The speed of the ball will be the same for all ramps.

Question 37

Choose the one alternative that best completes the statement or answers the question.
A heavy dart and a light dart are launched vertically by identical ideal springs. Both springs were initially compressed by the same amount. There is no significant air resistance. Which of the
Following statements about these darts are correct? (There could be more than one correct choice.)

A) The light dart goes higher than the heavy dart.
B) At the maximum height, both darts have the same gravitational potential energy.
C) Both darts began moving upward with the same initial speed.
D) The heavy dart goes higher than the light dart.
E) Both darts reach the same maximum height.

Question 38

Choose the one alternative that best completes the statement or answers the question.
A girl throws a stone from a bridge. Consider the following ways she might throw the stone. The speed of the stone as it leaves her hand is the same in each case.
Case A: Thrown straight up.
Case B: Thrown straight down.
Case C: Thrown out at an angle of 45° above horizontal.
Case D: Thrown straight out horizontally.
In which case will the speed of the stone be greatest when it hits the water below if there is no
Significant air resistance?

A) Case A
B) Case B
C) Case C
D) Case D
E) The speed will be the same in all cases.

Question 39

Choose the one alternative that best completes the statement or answers the question.
A heavy sled and a light sled, both moving horizontally with the same speed, suddenly slide onto a rough patch of snow and eventually come to a stop. The coefficient of kinetic friction between the
Sleds and the rough snow is the same for both of them. Which of the following statements about
These sleds are correct? (There could be more than one correct choice.)

A) The friction from the snow will do the same amount of work on both sleds.
B) Both sleds will slide the same distance on the rough snow before stopping.
C) The heavy sled will slide farther on the rough snow than the light sled.
D) The light sled will slide farther on the rough snow than the heavy sled.
E) The friction from the snow will do more negative work on the heavy sled than on the light sled.

Question 40

Choose the one alternative that best completes the statement or answers the question.
A person stands on the edge of a cliff. She throws three identical rocks with the same speed. Rock X is thrown vertically upward, rock Y is thrown horizontally, and rock Z is thrown vertically
Downward. If the ground at the base of the cliff is level, which rock hits the ground with the
Greatest speed if there is no air resistance?

A) Rock X
B) Rock Y
C) Rock Z
D) They all hit the ground with the same speed.

Question 41

Choose the one alternative that best completes the statement or answers the question.
A 3.0-kg brick rests on a perfectly smooth ramp inclined at 34° above the horizontal. The brick is kept from sliding down the plane by an ideal spring that is aligned with the surface and attached
To a wall above the brick. The spring has a spring constant (force constant) of 120 N/m. By how
Much does the spring stretch with the brick attached?

A) 24 cm
B) 240 cm
C) 14 cm
D) 36 cm
E) 360 cm

Question 42

Choose the one alternative that best completes the statement or answers the question.
An object attached to a spring is pulled across a horizontal frictionless surface. If the force constant (spring constant) of the spring is 45 N/m and the spring is stretched by 0.88 m when the object is accelerating at $1.4 \mathrm {~m} / \mathrm { s } ^ { 2 }$
what is the mass of the object?

A) 31 kg
B) 36 kg
C) 24 kg
D) 28 kg

Question 43

Choose the one alternative that best completes the statement or answers the question.
You carry a 7.0-kg bag of groceries 1.2 m above the ground at constant speed across a 2.7 m room. How much work do you do on the bag in the process?

A) 157 J
B) 0.00 J
C) 185 J
D) 82 J

Question 44

Write the word or phrase that best completes each statement or answers the question.
A very light ideal spring with a spring constant (force constant) of 2.5 N/cm pulls
horizontally on an 18-kg box that is resting on a horizontal floor. The coefficient of static
friction between the box and the floor is 0.65, and the coefficient of kinetic friction is 0.45.
(a) How long is the spring just as the box is ready to move?
(b) If the spring pulls the box along with a constant forward velocity of 1.75 m/s, how long
is the spring?
(c) How long is the spring if it pulls the box forward at a constant 2.75 m/s?

Question 45

Choose the one alternative that best completes the statement or answers the question.
How much work would a child do while pulling a 12-kg wagon a distance of 4.3 m with a 22 N force?

A) 95 J
B) 67 J
C) 52 J
D) 109 J

Question 46

Choose the one alternative that best completes the statement or answers the question.
It requires 0.30 kJ of work to fully drive a stake into the ground. If the average resistive force on the stake by the ground is 828 N, how long is the stake?

A) 0.41 m
B) 0.23 m
C) 0.36 m
D) 0.31 m

Question 47

Choose the one alternative that best completes the statement or answers the question.
An ornament of mass 40.0 g is attached to a vertical ideal spring with a force constant (spring constant) of 20.0 N/m. The ornament is then lowered very slowly until the spring stops stretching. How much does the spring stretch?

A) 0.0816 m
B) 0.00200 m
C) 0.0196 m
D) 0.800 m
E) 0.200 m

Question 48

Choose the one alternative that best completes the statement or answers the question.
Matthew pulls his little sister Sarah along the horizontal ground in a wagon. He exerts a force on the wagon of 60.0 N at an angle of $37.0 ^ { \circ }$ above the horizontal. If he pulls her a distance of 12.0 m, how much work does Matthew do?

A) 185 J
B) 575 J
C) 433 J
D) 720 J

Question 49

Write the word or phrase that best completes each statement or answers the question.
A very light ideal spring having a spring constant (force constant) of 8.2 N/cm is used to lift a 2.2-kg tool with an upward acceleration of $3.25 \mathrm {~m} / \mathrm { s } ^ { 2 }$

If the spring has negligible length when it us not stretched, how long is it while it is pulling the tool upward?

Question 50

Choose the one alternative that best completes the statement or answers the question.
A 30-N box is pulled upward 6.0 m along the surface of a ramp that rises at $37 ^ { \circ }$ above the horizontal. How much work does gravity do on the box during this process?

A) -110 J
B) -140 J
C) -1100 J
D) -180 J
E) 120 J

Question 51

Choose the one alternative that best completes the statement or answers the question.
Find the net work done by friction on a box that moves in a complete circle of radius 1.82 m on a uniform horizontal floor. The coefficient of kinetic friction between the floor and the box is 0.25 , and the box weighs 65.0 N

A) 1800 J
B) 370 J
C) 0 J
D) 190 J

Question 52

Write the word or phrase that best completes each statement or answers the question.
A very light ideal spring of spring constant (force constant) 2.5 N/cm is 15 cm long when
nothing is attached to it. It is now used to pull horizontally on a 12.5-kg box on a perfectly
smooth horizontal floor. You observe that the box starts from rest and moves 96 cm during
the first 1.6 s of its motion with constant acceleration. How long is the spring during this
motion?

Question 53

Choose the one alternative that best completes the statement or answers the question.
A force of 30 N stretches a very light ideal spring 0.73 m from equilibrium. What is the force constant (spring constant) of the spring?

A) 34 N/m
B) 22 N/m
C) 46 N/m
D) 41 N/m

Question 54

Choose the one alternative that best completes the statement or answers the question.
A very light ideal spring stretches by 21.0 cm when it is used to hang a 135-N object. What is the weight of a piece of electronic equipment that would stretch the spring by 44.9 cm if you hung the
Equipment using the spring?

A) 289 N
B) 176 N
C) 405 N
D) 63 N

Question 55

Choose the one alternative that best completes the statement or answers the question.
A person carries a 25.0-N rock through the path shown in the figure, starting at point A and ending at point B . The total time from A to B is 1.50 min. How much work did gravity do on the rock between A and B ?

A) 75 J
B) 0 J
C) 275 J
D) 625 J
E) 20.0 J

Question 56

Choose the one alternative that best completes the statement or answers the question.
A child does 350 J of work while pulling a box from the ground up to his tree house at a steady speed with a light rope. The tree house is 4.0 m above the ground. What is the mass of the box?

A) 5.3 kg
B) 6.7 kg
C) 8.9 kg
D) 8.0 kg

Question 57

Write the word or phrase that best completes each statement or answers the question.
A 500-kg elevator is pulled upward with a constant force of 5500 N for a distance of 50.0
m.
(a) What is the work done by the 5500-N force?
(b) What is the work done by gravity?
(c) What is the net work done on the elevator?

Question 58

Choose the one alternative that best completes the statement or answers the question.
A crane lifts a 425 kg steel beam vertically upward a distance of 95 m. How much work does the crane do on the beam if the beam accelerates upward at 1.8 m/s²? Neglect frictional forces.

A) $3.2 \times 10 ^ { 5 } \mathrm {~J}$
B) $4.7 \times 10 ^ { 5 } \mathrm {~J}$
C) $4.0 \times 10 ^ { 5 } \mathrm {~J}$
D) $2.7 \times 10^5 \mathrm{\jmath}$

Question 59

Write the word or phrase that best completes each statement or answers the question.
A 2.0-kg object is lifted vertically through 3.00 m by a 150-N force. How much work is done on the object by gravity during this process?

Question 60

Choose the one alternative that best completes the statement or answers the question.
A traveler pulls on a suitcase strap at an angl $36 ^ { \circ }$ above the horizontal. If 555 J of work are done by the strap while moving the suitcase a horizontal distance of 15 m, what is the tension in the
Strap?

A) 46 N
B) 52 N
C) 37 N
D) 56 N

Question 61

Write the word or phrase that best completes each statement or answers the question.
$$\text { How fast must a } 6.0 - \mathrm { kg } \text { cat run to have a kinetic energy of } 150 \mathrm {~J} \text { ? }$$

Question 62

Choose the one alternative that best completes the statement or answers the question.
A force acts on an object, causing it to move parallel to the force. The graph in the figure shows this force as a function of the position of the object. How much work does the force do as the object moves from 6 m to 12 m ?

A) 20 J
B) 70 J
C) 40 J
D) 0 J
E) 30 J

Question 63

Choose the one alternative that best completes the statement or answers the question.
A 1000-kg car experiences a net force of 9500 N while slowing down from 30 m/s to 15.9 m/s. How far does it travel while slowing down?

A) 31 m
B) 34 m
C) 37 m
D) 41 m

Question 64

Choose the one alternative that best completes the statement or answers the question.
A force acts on an object, causing it to move parallel to the force. The graph in the figure shows this force as a function of the position of the object. How much work does the force do as the object moves from 0 to 15 m?

A) 25 J
B) 125 J
C) 100 J
D) 50 J
E) 150 J

Question 65

Choose the one alternative that best completes the statement or answers the question.
A 1.0-kg object moving in a certain direction has a kinetic energy of 2.0 J. It hits a wall and comes back with half its original speed. What is the kinetic energy of this object at this point?

A) 0.25 J
B) 0.50 J
C) 1.0 J
D) 2.0 J
E) 4.0 J

Question 66

Choose the one alternative that best completes the statement or answers the question.
A force acts on an object, causing it to move parallel to the force. The graph in the figure shows this force as a function of the position of the object. How much work does the force do as the object moves from 0 m to 4 m?

A) 70 J
B) 30 J
C) 0 J
D) 40 J
E) 20 J

Question 67

Choose the one alternative that best completes the statement or answers the question.
How large a net force is required to accelerate a 1600-kg SUV from rest to a speed of 25 m/s in a distance of 200 m?

A) 0 N
B) 2500 N
C) 400 N
D) 1600 N
E) 200 N

Question 68

Choose the one alternative that best completes the statement or answers the question.
A person carries a 2.00-N pebble through the path shown in the figure, starting at point A and ending at point B . The total time from A to B is 6.75 min. How much work did gravity do on the rock between A and B ?

A) -56.0 J
B) -30.0 J
C) -36.0 J
D) 56.0 J
E) 30.0 J

Question 69

Choose the one alternative that best completes the statement or answers the question.
The net force that an animal exerts on a large piece of fruit it has found is observed and is shown in the graph in the figure. If the force is parallel to the motion of the fruit, how much work did the animal do during the encounter?

A) 50 J
B) 0 J
C) 22 J
D) 25 J
E) 12.5 J

Question 70

Choose the one alternative that best completes the statement or answers the question.
The resultant force on an object over a 0.50-s time interval is plotted in the graph in the figure. How much work did this force do on the object during the 0.50-s interval?

A) 12.5 J
B) 22 J
C) -25 J
D) 50 J
E) 0 J

Question 71

Choose the one alternative that best completes the statement or answers the question.
When a car of mass 1167 kg accelerates from 10.0 m/s to some final speed, $4.00 \times 10 ^ { 5 } \mathrm {~J}$ of work are done. Find this final speed.

A) 30.8 m/s
B) 25.2 m/s
C) 22.4 m/s
D) 28.0 m/s

Question 72

Choose the one alternative that best completes the statement or answers the question.
A stone with a mass of 1.0 kg is tied to the end of a light string which keeps it moving in a circle with a constant speed of 4.0 m/s on a perfectly smooth horizontal tabletop. The radius of the path is 0.60 m. How much work does the tension in the string do on the stone as it makes one-half of a complete circle?

A) 0 J
B) 80 J
C) 40 J
D) 3.8 J
E) 100 J

Question 73

Choose the one alternative that best completes the statement or answers the question.
How much work must be done by frictional forces in slowing a 1000-kg car from 26.1 m/s to rest?

A) $3.41 \times 10 ^ { 5 } \mathrm {~J}$
B) $2.73 \times 10 ^ { 5 } \mathrm {~J}$
C) $4.77 \times 10 ^ { 5 } \mathrm {~J}$
D) $4.09 \times 10 ^ { 5 } \mathrm {~J}$

Question 74

Choose the one alternative that best completes the statement or answers the question.
A 100-N force has a horizontal component of 80 N and a vertical component of 60 N. The force is applied to a cart on a level frictionless floor. The cart starts from rest and moves 2.0 m horizontally
Along the floor due to this force. What is the cart's final kinetic energy?

A) 120 J
B) 160 J
C) zero
D) 200 J

Question 75

Choose the one alternative that best completes the statement or answers the question.
A 1000-kg car is moving at 15 km/h. If a 2000-kg truck has 23 times the kinetic energy of the car, how fast is the truck moving?

A) 72 km/h
B) 41 km/h
C) 51 km/h
D) 61 km/h

Question 76

Choose the one alternative that best completes the statement or answers the question.
An object hits a wall and bounces back with half of its original speed. What is the ratio of the final kinetic energy to the initial kinetic energy of the object?

A) 1/2
B) 1/8
C) 1/4
D) 1/16

Question 77

Choose the one alternative that best completes the statement or answers the question.
How much kinetic energy does a 0.30-kg stone have if it is thrown at 44 m/s?

A) 290 J
B) 510 J
C) 440 J
D) 580 J

Question 78

Choose the one alternative that best completes the statement or answers the question.
What is the minimum energy needed to change the speed of a 1600-kg sport utility vehicle from 15.0 m/s to 40.0 m/s?

A) 1.10 MJ
B) 40.0 kJ
C) 10.0 kJ
D) 0.960 MJ
E) 20.0 kJ

Question 79

Choose the one alternative that best completes the statement or answers the question.
A 10-kg dog is runnng with a speed of 5.0 m/s. What is the minimum work required to stop the dog in 2.40 s?

A) 125 J
B) 100 J
C) 50 J
D) 75 J

Question 80

Choose the one alternative that best completes the statement or answers the question.
A force acts on an object, causing it to move parallel to the force. The graph in the figure shows this force as a function of the position of the object. How much work does the force do as the object moves from 4 m to 6 m?

A) 30 J
B) 0 J
C) 20 J
D) 70 J
E) 40 J