Question 1

A soccer ball (mass = 0.43 kg)is moving at a speed of 20 m/s when it is kicked with a force of 300 N resulting in it going in the opposite direction with the same speed as before.What is the magnitude of the impulse delivered to the ball?

Accepted Answer

A)   0,because the before and after momenta cancel each other.
B)   8.6 kg·m/s
C)   17 kg·m/s
D)   2 600 kg·m/s C

Question 2

A 30-kg object sitting at rest is struck elastically in a head-on collision with a 10-kg object initially moving at +3.0 m/s.Find the final velocity of the 30 kg object after the collision.

Accepted Answer

A)   −1.0 m/s
B)   +1.2 m/s
C)   +1.5 m/s
D)   +2.0 m/s C

Question 3

A miniature spring-loaded,radio-controlled gun is mounted on an air puck.The gun's bullet has a mass of 5.00 g,and the gun and puck have a combined mass of 130g.With the system initially at rest,the radio controlled trigger releases the bullet causing the puck and empty gun to move with a speed of 0.500 m/s.What is the bullet's speed?

Accepted Answer

A)   4.80 m/s
B)   13.0 m/s
C)   48.0 m/s
D)   12.5 m/s B

Question 4

A 0.10-kg object moving initially with a velocity of +0.20 m/s makes an elastic head-on collision with a 0.15-kg object initially at rest.What percentage of the original kinetic energy is gained by the 0.15-kg object?

Accepted Answer

A)   4%
B)   −4%
C)   50%
D)   96%

Question 5

A 2500-kg truck moving at 10.00 m/s strikes a car waiting at a traffic light,hooking bumpers.The two continue to move together at 6.00 m/s.What was the mass of the struck car?

Accepted Answer

A)   1730 kg
B)   1670 kg
C)   1200 kg
D)   1070 kg

Question 6

A 90-kg halfback running north with a speed of 10 m/s is tackled by a 120-kg opponent running south at 5.0 m/s.The collision is perfectly inelastic.Compute the velocity of the two players just after the tackle.

Accepted Answer

A)   1.4 m/s south
B)   2.8 m/s south
C)   2.8 m/s north
D)   1.4 m/s north

Question 7

A 75-kg swimmer dives horizontally off a 500-kg raft.The diver's speed immediately after leaving the raft is 1.6 m/s.A micro-sensor system attached to the edge of the raft measures the time interval during which the diver applies an impulse to the raft just prior to leaving the raft surface.If the time interval is read as 0.20 s,what is the magnitude of the average horizontal force by diver on the raft?

Accepted Answer

A)   900 N
B)   450 N
C)   600 N
D)   1500 N

Question 8

A billiard ball (Ball #1)moving at 5.00 m/s strikes a stationary ball (Ball #2)of the same mass.After the elastic collision,Ball #1 moves at a speed of 3.50 m/s.Find the speed of Ball #2 after the collision.

Accepted Answer

A)   1.25 m/s
B)   1.50 m/s
C)   2.16 m/s
D)   3.57 m/s

Question 9

A 1.00-kg duck is flying overhead at 1.50 m/s when a hunter fires straight up.The 0.0100-kg bullet is moving 200 m/s when it hits the duck and stays lodged in the duck's body.What is the speed of the duck and bullet immediately after the hit?

Accepted Answer

A)   1.49 m/s
B)   1.80 m/s
C)   2.48 m/s
D)   2.50 m/s

Question 10

A 70-kg man is standing in a 20-kg boat.Thinking he is stepping out onto the dock,the man steps to the right.However,the following will actually happen (ignore the friction of the water or air on the boat or the man):

Accepted Answer

A)   The man only moves a short distance to the right while the boat moves a larger distance to the left.
B)   The man actually stays still while the boat moves toward the left.
C)   The boat doesn't move and the man moves to the right.
D)   None of the above.

Question 11

A baseball infielder,mass 75.0 kg,jumps up with velocity 2.00 m/s and catches a 0.150-kg baseball moving horizontally at 50.0 m/s.Of the following,which is closest to the final momentum of the system,infielder and baseball?

Accepted Answer

A)   158 kg m/s
B)   155 kg m/s
C)   152 kg m/s
D)   150 kg m/s

Question 12

A miniature,spring-loaded,radio-controlled gun is mounted on an air puck.The gun's bullet has a mass of 5.00 g,and the gun and puck have a combined mass of 130g.With the system initially at rest,the radio-controlled trigger releases the bullet,causing the puck and empty gun to move with a speed of 0.500 m/s.Of the total kinetic energy of the gun-puck-bullet system,what percentage is in the bullet?

Accepted Answer

A)   50%
B)   96%
C)   3.4%
D)   100%

Question 13

Lonnie pitches a baseball of mass 0.15 kg.The ball arrives at home plate with a speed of 40 m/s and is batted straight back to Lonnie with a return speed of 60 m/s.If the bat is in contact with the ball for 0.050 s,what is the impulse experienced by the ball?

Accepted Answer

A)   360 N·s
B)   20 N·s
C)   400 N·s
D)   15 N·s

Question 14

Popeye,of mass 70 kg,has just downed a can of spinach.He accelerates quickly and stops Bluto,of mass 700 kg (Bluto is very dense),who is charging in at 5.0 m/s.What was Popeye's remarkable speed?

Accepted Answer

A)   10 m/s
B)   31 m/s
C)   50 m/s
D)   100 m/s

Question 15

Alex throws a 0.15-kg rubber ball down onto the floor.The ball's speed just before impact is 6.5 m/s and just after is 3.5 m/s.If the ball is in contact with the floor for 0.050 s,what is the magnitude of the average force applied by the floor on the ball?

Accepted Answer

A)   60 N
B)   133 N
C)   30 N
D)   3.5 N

Question 16

During a snowball fight,two balls with masses of 0.4 and 0.6 kg,respectively,are thrown in such a manner that they meet head-on and combine to form a single mass.The magnitude of initial velocity for each is 20 m/s.What is the speed of the 1.0-kg mass immediately after collision?

Accepted Answer

A)   zero
B)   3 m/s
C)   4 m/s
D)   5 m/s

Question 17

A 20-g bullet moving at 1000 m/s is fired through a one-kg block of wood emerging at a speed of 200 m/s.If the block had been originally at rest and is free to move,what is its resulting speed?

Accepted Answer

A)   800 m/s
B)   80 m/s
C)   16 m/s
D)   8 m/s

Question 18

A 75-kg swimmer dives horizontally off a 250-kg raft initially at rest.If the diver's speed immediately after leaving the raft is 2 m/s,what is the corresponding raft speed?

Accepted Answer

A)   0.2 m/s
B)   0.3 m/s
C)   0.6 m/s
D)   4.0 m/s

Question 19

Two skaters,both of mass 75 kg,are initially at rest on skates on a frictionless ice pond.One skater throws a 0.3-kg ball at 10 m/s to his friend,who catches it and throws it back at 10 m/s.When the first skater has caught the returned ball,what is the velocity of each of the two skaters?

Accepted Answer

A)   0.08 m/s,moving apart
B)   0.04 m/s,moving apart
C)   0.08 m/s,moving towards each other
D)   0.04 m/s,moving towards each other

Question 20

In an inelastic collision between two objects with unequal masses:

Accepted Answer

A)   the velocity of one will increase by the amount that the velocity of the other decreases.
B)   the momentum of one will increase by the amount that the momentum of the other decreases.
C)   the energy of one increases by the amount that the energy of the other decreases.
D)   the total momentum of the system will decrease.

Exam 7: Rotational Motion and the Law of Gravity: Part A

A soccer ball (mass = 0.43 kg) is moving at a speed of 20 m/s when it is kicked with a force of 300 N resulting in it going in the opposite direction with the same speed as before.What is the magnitude of the impulse delivered to the ball?