Question 1

The impulse delivered to an object is equal to the change in the object's velocity.

Accepted Answer

A) True 
 B)False

Question 2

Identical forces act for the same length of time on two different masses. The change in momentum of the smaller mass is

Accepted Answer

A)  smaller than the change in momentum of the larger mass, but not zero. 
B)  larger than the change in momentum of the larger mass. 
C)  equal to the change in momentum of the larger mass. 
D)  zero. 
E)  There is not enough information to answer the question.

Question 3

A 310-g air track cart is traveling at 1.25 m/s and a 260-g cart traveling in the opposite direction at 1.33 m/s. What is the speed of the center of mass of the two carts?

Accepted Answer

A)  2.80 m/s 
B)  0.0732 m/s 
C)  0.131 m/s 
D)  1.47 m/s 
E)  1.29 m/s

Question 4

Jennifer hits a stationary 200. gram ball and it leaves the racket at 40. m/s. If time lapse photography shows that the ball was in contact with the racket for 40. ms:
(a) What average force was exerted on the racket?
(b) What is the ratio of this force to the weight of the ball?

Accepted Answer

The answer of Jennifer hits a stationary 200. gram ball...

Question 5

A 0.140-kg baseball is dropped and reaches a speed of 1.20 m/s just before it hits the ground. It rebounds with a speed of 1.00 m/s. What is the change of the ball's momentum?

Accepted Answer

A)  0.0280 kg∙m/s upwards 
B)  0.0280 kg∙m/s downwards 
C)  0.308 kg∙m/s upwards 
D)  0.308 kg∙m/s downwards 
E)  0 kg∙m/s

Question 6

A batter hits a foul ball. The 0.140-kg baseball that was approaching him at 40.0 m/s leaves the bat at 30.0 m/s in a direction perpendicular to the line between the batter and the pitcher. What is the magnitude of the impulse delivered to the baseball?

Accepted Answer

A)  9.80 Ns 
B)  1.40 Ns 
C)  3.50 Ns 
D)  5.60 Ns 
E)  7.00 Ns

Question 7

A rocket develops 10,000 N of thrust at liftoff. If the speed of the ejected fuel is 2000 m/s, at what rate (in kg/s) must the fuel be ejected?

Accepted Answer

The answer of A rocket develops 10,000 N of thrust...

Question 8

A rope is held from one end in such a way that the lower end just touches a table. The rope is then lowered onto the table with constant velocity. The force that is needed to hold the upper end of the rope is

Accepted Answer

A)  equal to the weight of the portion of the rope that is not on the table. 
B)  greater than the weight of the portion of the rope that is not on the table. 
C)  less than the weight of the portion of the rope that is not on the table but not zero N. 
D)  zero N. 
E)  Cannot be determined without additional information.

Question 9

A rubber ball and a lump of putty have equal mass. They are thrown with equal speed against a wall. The ball bounces back with nearly the same speed with which it hit. The putty sticks to the wall. Which objects experiences the greater momentum change?

Accepted Answer

A)  the ball 
B)  the putty 
C)  Both experience the same non-zero momentum change. 
D)  Both experience zero momentum change. 
E)  Cannot be determined from the information given.

Question 10

Three masses are positioned as follows:
2.0 kg at (0, 0); 2.0 kg at (2, 0); and 4.0 kg at (2,1).
Determine the coordinates of the center of mass.

Accepted Answer

The answer of Three masses are positioned as follows:
2.0 kg...

Question 11

An object that is initially at rest breaks up into two pieces of unequal masses when a spring-loaded device is released. If you compare the kinetic energy of the larger mass to that of the smaller mass immediately after they separate, which of the following statements is correct?

Accepted Answer

A)  The kinetic energy of the larger mass is greater. 
B)  The kinetic energy of the smaller mass is greater. 
C)  The kinetic energies of the two masses are equal. 
D)  The total kinetic energy is zero J.

Question 12

A plate falls vertically to the floor and breaks up into three pieces, which slide along the floor. Immediately after the impact, a 320-g piece moves along the x-axis with a speed of 2.00 m/s and a 355-g piece moves along the y-axis with a speed of 1.50 m/s. The third piece has a mass of 100 g. In what direction does the third piece move?

Accepted Answer

A)  216.9° from the x-axis 
B)  219.8° from the x-axis 
C)  36.9° from the x-axis 
D)  39.9° from the x-axis 
E)  39.8° from the x-axis

Question 13

Internal forces cannot change the total momentum of a system.

Accepted Answer

A) True 
 B)False

Question 14

A 900-kg car traveling east at 15.0 m/s collides with a 750-kg car traveling north at 20.0 m/s. The cars stick together.
(a) What is the speed of the wreckage just after the collision?
(b) In what direction does the wreckage move just after the collision?

Accepted Answer

The answer of A 900-kg car traveling east at 15.0...

Question 15

In space there is nothing for the rocket to "push against" so how does it accelerate?

Accepted Answer

The answer of In space there is nothing for the...

Question 16

A plate falls vertically to the floor and breaks up into three pieces, which slide along the floor. Immediately after the impact, a 200-g piece moves along the x-axis with a speed of 2.00 m/s, a 235-g piece moves along the y-axis with a speed of 1.50 m/s. The third piece has a mass of 100 g. What is its speed?

Accepted Answer

A)  2.51 m/s 
B)  2.57 m/s 
C)  3.50 m/s 
D)  5.33 m/s 
E)  6.83 m/s

Question 17

A 2.00-g bullet hits and becomes embedded in a 5.00-kg wood block which is hanging from a 1.20-m long string. This causes the block to swing through an arc of 3.50°. What was the speed of the bullet before it hit the block?

Accepted Answer

A)  16.7 m/s 
B)  524 m/s 
C)  25.3 m/s 
D)  262 m/s 
E)  789 m/s

Question 18

A 50-gram ball moving +10 m/s collides head-on with a stationary ball of mass 100.g. The collision is elastic. What is the speed of each ball immediately after the collision?

Accepted Answer

The answer of A 50-gram ball moving +10 m/s collides...

Question 19

A 0.330-kg volleyball is dropped from rest. It takes it 1.30 s to reach the ground. What is the magnitude of its momentum just before it hits the ground?

Accepted Answer

A)  4.21 kg∙m/s 
B)  0.429 kg∙m/s 
C)  3.24 kg∙m/s 
D)  2.11 kg∙m/s 
E)  1.18 kg∙m/s

Question 20

An elastic collision of two objects is characterized by the following.

Accepted Answer

A)  Total momentum of the system is conserved. 
B)  Total kinetic energy of the system remains constant. 
C)  Both A and B are true. 
D)  Neither A nor B are true.

Exam 9: Linear Momentum and Collisions