Chapter 4
19 ) A piece of putty moving with 1 unit of momentum strikes and sticks to a heavy bowling ball that is initially at rest . After the putty sticks to the ball , both move with a combined momentum of A ) less than 1 unit . B ) more than 1 unit . C ) 1 unit . D ) not enough information given
) not enough information Answer : C
12 ) When you are in the way of a fast - moving object and can't get out of its way , you will suffer a smaller force of impact if you decrease its momentum over a A ) long time . B ) short time . C ) long time OR short time ( same way either way ) .
Answer : A
16 ) A 4 - kg ball has a momentum of 12 kg m / s . What is the ball's speed ? A ) 3 m / s B ) 4 m / s . C ) 12 m / s D ) 48 m / s E ) none of the above
Answer : A
18 ) A heavy truck and a small car rolling down a hill at the same speed are forced to stop in the same amount of time . Compared to the force that stops the car , the force needed to stop the truck is A ) greater . B ) smaller C ) the same .
Answer : A
21 ) Two billiard balls having the same mass roll toward each other , each moving at the same speed . What is the combined momentum of the two balls ? A 0 kg . m / s B ) 10 kg m / s C ) more information needed to determine
Answer : A
28 ) If you push for an hour against a stationary wall , no work is done A ) on the wall . B at all . C ) both A and B D ) none of the above
Answer : A
6 ) The impulse - momentum relationship is a irect result A ) Newton's First Law . B ) Newton's Second Law . C ) Newton's Third Law .
Answer : B
43 ) When a car is braked to a stop , its kinetic energy is transformed to A ) stopping energy . B ) potential energy . C ) energy of motion . D ) energy of rest . E ) heat .
Answer : E
15 ) Compared with falling on a wooden floor , a wine glass may not break when it falls to a carpeted floor because of the A ) lesser impulse in stopping . B ) longer time to stop . C ) both A and B D ) neither A nor B Answer :
B
17 ) A ball is moving at 4 m / s and has a momentum of 48 kg m / s . What is the ball's mass ? A ) 4 kg B 12 kg C ) 48 kg D ) 192 kg E ) none of the above Answer
B
48 ) It takes 40 J of work 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 Answer
B.
13 ) Padded dashboards in cars are safer in an accident than nonpadded ones because an occupant hitting the dash has A ) increased time of impact . B ) decreased impulse . C ) decreased impact force . D ) both A and B E ) both A and C 14 ) The force on an apple hitting the ground depends upon A ) the speed of the apple just before it hits . B ) the time of impact with the ground . C ) Both A and B. Answer
C
22 ) A 5 - kg fish swimming at a speed of 1 m / s swallows an absent - minded 1 - kg fish at rest . The speed of the larger fish after lunch is A ) 1/2 m / s B ) 2/5 m / s . C ) 5/6 m D ) 6/5 m / s . E ) 1 m / s . Answer
C
27 ) The average momentum of a 70 - kg runner who covers 400 m in 50 s is A ) 8.75 kg . m / s . B ) 57 kg . m / s . C ) 560 kg . m / s . D ) 5490 kg m / s . Answer
C
50 ) A 2 - kg mass has 40 J of potential energy with respect to the ground . Approximately how far is it located above the ground ? A ) I m B ) 2 m C ) 3 m D ) 4 m E ) none of the above .
Answer : B
51 ) Using 1000 J of work , a toy elevator is raised from the ground floor to the second floor in 20 s . How much power does the elevator use ? A ) 20 W B ) 50 W C ) 100 W D ) 1000 W E ) 20,000 W
Answer : B
52 ) Two identical arrows , one with twice the kinetic energy of the other , are fired into a hay bale . The faster arrow will penetrate A ) the same distance as the slower arrow . B ) twice as far as the slower arrow . C ) four times as far as the slower arrow . D ) more than four times as far as the slower arrow . E ) none of the above .
Answer : B
2 ) A freight train rolls along a track with considerable momentum . If it rolls at the same speed but has twice as much mass , its momentum is A ) zero . B ) doubled . C ) quadrupled . D ) unchanged .
Answer : B.
10 ) In order to catch a ball , a baseball player extends the hand forward before impact with the ball and then lets it ride backward in the direction of the ball's motion upon impact . Doing this reduces the force of impact on the player's hand principally because the A ) force of impact is reduced . B ) relative velocity is less . C ) time of impact is increased . D ) time of impact is decreased . E ) none of the above
Answer : C
38 ) A 1000 - kg car and a 2000 - kg car are hoisted the same distance in a gas station . Raising the more massive car requires A ) less work . B ) as much work . C ) twice as much work . D ) four times as much work . E ) more than four times as much work
Answer : C
44 ) No work is done by gravity on a bowling ball that rolls along a bowling alley because A ) no force acts on the ball . B ) no distance is covered by the ball . C ) the force on the ball is at right angles to the ball's motion . D ) no potential energy is being converted to kinetic energy . E ) its kinetic energy remains constant .
Answer : C
45 ) Which requires more work : lifting a 50 - kg sack vertically 2 m or lifting a 25 - kg sack vertically 4 m ? A ) lifting the 50 - kg sack B ) lifting the 25 - kg sack C ) Both require the same amount of work .
Answer : C
46 ) A 50 - kg sack is lifted 2 m in the same time as a 25 - kg sack is lifted 4 m . The power expended in raising the 50 - kg sack compared to the power used to lift the 25 - kg sack is A ) twice as much . B ) half as much . C ) the same .
Answer : C
7 ) A cannon recoils from firing a cannonball . The speed of the cannon's recoil is small because the A ) force against the cannon is smaller than against the ball . B ) momentum is mainly concentrated in the ball . C ) cannon has more mass than the ball . D ) momentum of the cannon smaller .
Answer : C
8 ) Two objects , A and B , have the same size and shape , but A is twice as heavy as B. When they are dropped simultaneously from a tower , they reach the ground at the same time , but A has greater A ) speed . B ) acceleration . C ) momentum . D ) all of the above E ) none of the above
Answer : C
29 ) If you push an object twice as far while applying the same force , you do A ) twice as much work . B ) four times as much work . C ) the same amount of work .
Answer A
30 ) If you push an object just as far while applying twice the force , you do A ) twice as much work . B ) four times as much work . C ) the same amount of work .
Answer : A
34 ) If you exert 1 N for a distance of 1 m in 1 s , you will deliver a power of A ) 1 W. B ) 2 W. C ) 1/3 W. D ) 3 W. E ) none of the above
Answer : A
24 ) A 1 - kg chunk of putty moving at 1 m / s collides with and sticks to a 5 - kg bowling ball that is initially at rest . The bowling ball and putty are then set in motion with a speed of A ) 1/4 m / s . B ) 1/5 m / s . C ) 1/6 m / s . D ) none of the above E ) not enough information given
Answer : C
25 ) You're driving down the highway and a bug spatters on your windshield . Which undergoes the greater change in momentum ? A ) the bug B ) your car C ) both the same
Answer : C
26 ) A 5000 - kg freight car runs into a 10,000 - kg freight car at rest . They couple upon collision and move with a speed of 2 m / s . What was the initial speed of the 5000 - kg car ? A ) 4 m / s B ) 5 m / s C ) 6 m / s D ) 8 m / s E ) none of the above
Answer : C
3 ) A moving object on which no forces are acting will continue to move with constant A ) acceleration . B ) impulse . C ) momentum . D ) all of the above E ) none of the above
Answer : C
31 ) If you push an object with twice the work input for twice the time , your power input is A ) twice as much . B ) four times as much . C ) the same amount .
Answer : C
33 ) If you do work on an object in half the time , your power output is A ) half the usual power output . B ) the same power output . C ) twice the usual power output .
Answer : C
35 ) If you exert 100 J in 50 s , your power output is A ) 1/4 W. B ) 1/2 W. C ) 2 W. D ) 4 W. E ) more than 4 W.
Answer : C
36 ) When an object is lifted 10 m , it gains a certain amount of potential energy . If the same object is lifted 20 m , its potential energy gain is A ) less . B ) the same . C ) twice as much . D ) four times as much . E ) more than four times as much .
Answer : C
39 ) An object that has kinetic energy must be A ) moving . B ) falling C ) at an elevated position . D ) at rest . E ) none of the above
Answer : A
41 ) Bullets are fired from an airplane in the forward direction of motion . The momentum of the airplane will be A ) decreased . B ) unchanged . C ) increased .
Answer : A
20 ) A 1 - kg chunk of putty moving at 1 m / s collides and sticks to a 5 - kg bowling ball initially at rest . The bowling ball and putty then move with a momentum of A ) 0 kg . m B ) 1 kg m / s . C ) 2 kg . m / s . D ) 5 kg . m / s . E ) more than 5 kg . m / s .
Answer : B
32 ) A job is done slowly , while 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
Answer : B
4 ) Impulse and impact force involves the A ) distance the force acts . B ) time the force acts . C ) difference between acceleration and velocity . D ) mass and its effect on resisting a change in momentum .
Answer : B
5 ) It is correct to say that impulse is equal to A ) momentum . B ) the change in momentum . the force multiplied by the distance the force acts . D ) all of the above E ) none of the above
Answer : B
9 ) A heavy truck and a small truck roll down a hill . Neglecting friction , at the bottom of the hill , the heavy truck will have greater A ) speed . B ) acceleration . C ) momentum . D ) all of the above E ) none of the above
Answer : C
When you jump from an elevated position , you usually bend your knees upon reaching the ground By doing this , the time of the impact is about ten times more than for a stiff legged landing In this way , the average force your body experiences is reduced by A ) less than ten times . B ) more than ten times . C about ten times
Answer : C
40 ) An object that has potential energy may have this energy because of its A ) speed . ) acceleration . C ) momentum . D ) location . E ) none of the above
Answer : D
47 ) A TV set is pushed a distance of 2 m with a force of 20 N that is in the same direction as the set moves . How much work is done on the set ? A 2 J B ) 10 J C ) 20 J D ) 40 J E ) 80 J
Answer : D
13 ) Padded dashboards in cars are safer in an accident than nonpadded ones because an occupant hitting the dash has A ) increased time of impact . B ) decreased impulse . C ) decreased impact force . D ) both A and B E ) both A and C
Answer : E
largest A ) a tightrope walker crossing Niagara Falls B ) a pickup truck speeding along a highway C ) a Mack truck parked in a parking lot D ) the Science building on campus ) a dog running down the street
Answer B
49 ) A 2 - kg mass is held 4 m above the ground . What is the approximate potential energy of the mass with respect to the ground ? A ) 20 J B ) 40 J C ) 60 J D ) 80 J E ) none of the above .
Answer D