Physics 101 Practice Quiz 8

Practice Quiz 8
1)  A 0.140-kg baseball is dropped from rest from a height of 1.8 m above the ground. It rebounds to a
height of 1.4 m. What change in the ball's momentum occurs when the ball hits the ground?
A) 0.117 kg•m/s upwards
B) 0.117 kg•m/s downwards
C) 1.57 kg•m/s upwards
D) 0.350 kg•m/s upwards
Answer: C
2)  Two different masses have equal, non-zero kinetic energies. The momentum of the smaller mass is  
A) smaller than the momentum of the larger mass.
B) larger than momentum of the larger mass.
C) equal to the momentum of the larger mass.
D) There is not enough information to answer the question.
Answer: A
3)  In a collision between two unequal masses, how does the impulse imparted to the smaller mass by the
larger mass compare with the impulse imparted to the larger mass by the smaller one?
A) It is larger.
B) It is smaller.
C) They are equal.
D) The answer depends on how fast they are moving.
Answer: C
4)  Two ice skaters push off against one another starting from a stationary position. The 45-kg skater
acquires a speed of 0.375 m/s. What speed does the 60-kg skater acquire?
A) 0.500 m/s
B) 0.281 m/s
C) 0.375 m/s
D) 0 m/s
Answer: B
5)  An artillery shell explodes in midair and breaks up into many fragments. Which of the following
statements are true regarding conditions immediately before and immediately after the explosion:
I. The total momentum of the fragments is equal to the original momentum of the shell.
II. The total kinetic energy of the fragments is equal to the original kinetic energy of the shell.
A) Statement I only
B) Statement II only
C) Both Statement I and Statement II
D) Neither statement is true.
Answer: A
6)  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. In what direction does the wreckage move just after the collision?
A) 36.9e N of E
B) 42.0e N of E
C) 53.1e N of E
D) 48.0e N of E
Answer: D
7)  A 750-g mass traveling at 8.0 m/s undergoes a head-on elastic collision with a 50-g mass traveling
toward it also at 8.0 m/s. What is the speed of the 50-g mass after the collision?
A) 15 m/s
B) 4.0 m/s
C) 22 m/s  D) 0 m/s
Answer: C
8)  A 340-g air track cart traveling at 1.25 m/s collides elastically with a 300-g cart traveling in the opposite
direction at 1.33 m/s. What is the speed of the 300-g cart after the collision?
A) 2.80 m/s
B) 0.0693 m/s
C) 1.41 m/s
D) 1.29 m/s
Answer: C
9)  A 60.0-kg man stands at one end of a 20.0-kg uniform 10.0-m long board. How far from the man is the
center of mass of the man-board system?
A) 1.25 m
B) 2.50 m
C) 5.00 m
D) 7.50 m
Answer: A
10)  Three masses are located in the x-y plane as follows: a mass of 6 kg is located at (0 m, 0 m), a mass of
4 kg is located at (3 m, 0 m), and a mass of 2 kg is located at (0 m, 3 m). Where is the center of mass of the
system?
A) (1 m, 2 m)   B) (2 m, 1 m)   C) (1 m, 1 m)   D) (1 m, 0.5 m)
Answer: D
11)  An elastic 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: C
12)  A tennis ball undergoes an elastic collision when it hits the ground and bounces up. It is given that the
speed of the ball just before it hits the ground is -v0 and immediately after rebounding it is +v0. Which of
the statements below is true?
A) The momentum of the ball changes but the momentum of Earth does not.
B) The momentum of the ball changes and the momentum of Earth also changes.
C) The momentum of the ball does not change but the momentum of Earth changes.
D) Neither the momentum of the ball nor the momentum of Earth changes.
Answer: B
13)  You are standing at a bus stop holding an umbrella on a rainy day. While you wait for the bus the rain
shower turns into hail. Compared to the rain, the number of hail "drops" hitting the umbrella per second,
the mass of the "drops", and their speed all remain the same. The force you must exert to hold the umbrella
in the hail is
A) less than the force required in the rain.
B) the same as the force required in the rain.
C) more than the force required in the rain.
D) impossible to compare with the force required in the rain.
Answer: C
14)  A 750-g mass traveling at 8.0 m/s undergoes a head-on elastic collision with a 50-g mass traveling
toward it also at 8.0 m/s. What is the speed of the 50-g mass after the collision?
A) 15 m/s   B) 4.0 m/s   C) 22 m/s   D) 0 m/s
Answer: C