Practice Quiz 6 Momentum Collisions

1. 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 0.025 s, what is the
magnitude of the average force applied by the floor on the ball?
a. 60 N
b. 133 N
c. 3.0 N
d. 3.5 N
Answer A

2. A car wash nozzle directs a steady stream of water at 1.5 kg/s, with a speed of 30 m/s, against a
car window. What force does the water exert on the glass? Assume the water does not splash
back.
a. 11 N
b. 45 N
c. 110 N
d. 440 N
Answer B

3. The kinetic energy of an object is quadrupled. Its momentum will change by what factor?
a. zero
b. two
c. eight
d. four
Answer B

4. A lump of clay is thrown at a wall. A rubber ball of identical mass is thrown with the same
speed toward the same wall. Which statement is true?
a. The clay experiences a greater change in momentum than the ball.
b. The ball experiences a greater change in momentum than the clay.
c. The clay and the ball experience the same change in momentum.
d. It is not possible to know which object has the greater change in momentum.
Answer B

5. A railroad car of mass m and speed v collides and sticks to an identical railroad car that is initially at
rest. After the collision, the kinetic energy of the system
A) is the same as before.
B) is half as much as before.
C) is one third as much as before.
D) is one quarter as much as before.
Answer: B

6. An inelastic collision of two objects is characterized by the following.
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.
Answer: A

7. I drop a 60-g golf ball from 2.0 m high. It rebounds to 1.5 m. How much energy is lost?
a. 0.29 J
b. 0.50 J
c. 0.88 J
d. 1.0 J
Answer A

8. 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?
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
Answer: C

9. Two air track carts move along an air track towards each other. Cart A has a mass of 450 g and moves
toward the right with a speed of 0.850 m/s and air track cart B has a mass of 300 g and moves toward the
left with a speed of 1.12 m/s. What is the total momentum of the system?
A) 0.047 kg•m/s toward the right
B) 0.719 kg•m/s toward the right
C) 0.750 kg•m/s toward the right
D) 0.750 kg•m/s toward the left
Answer: A