Question 1

A stunt person jumps from the roof of a tall building, but no injury occurs because the person lands on a large, air-filled bag. Which one of the following best describes why no injury occurs?

Accepted Answer

A) The bag provides the necessary force to stop the person. 
B) The bag reduces the impulse to the person. 
C) The bag increases the amount of time the force acts on the person and reduces the change in momentum. 
D) The bag decreases the amount of time during which the momentum is changing and reduces the average force on the person. 
E) The bag increases the amount of time during which the momentum is changing and reduces the average force on the person.

Question 2

A comet fragment of mass 1.96 × 10S1U1P113S1S1P0 kg is moving at 6.50 × 10S1U1P14S1S1P0 m/s when it crashes into Callisto, a moon of Jupiter. The mass of Callisto is 1.08 × 10S1U1P123S1S1P0 kg. The collision is completely inelastic.
-Assuming for this calculation that Callisto's initial momentum is zero kg . m/s, what is the recoil speed of Callisto immediately after the collision?

Accepted Answer

A) 3.34 × 10-18 m/s 
B) 1.27 × 10-14 m/s 
C) 3.58 × 10-12 m/s 
D) 6.13 × 10-7 m/s 
E) 1.18 × 10-5 m/s

Question 3

Complete the following statement: A collision is elastic if

Accepted Answer

A) the final velocities are zero. 
B) the objects stick together. 
C) the final kinetic energy is zero. 
D) the final momentum is zero. 
E) the total kinetic energy is conserved.

Question 4

Complete the following statement: Momentum will be conserved in a two-body collision only if

Accepted Answer

A) both bodies come to rest. 
B) the collision is perfectly elastic. 
C) the kinetic energy of the system is conserved. 
D) the net external force acting on the two-body system is zero. 
E) the internal forces of the two body system cancel in action-reaction pairs.

Question 5

A 1.0-kg ball has a velocity of 12 m/s downward just before it strikes the ground and bounces up with a velocity of 12 m/s upward. What is the change in momentum of the ball?

Accepted Answer

A) zero kg .  m/s 
B) 12 kg .  m/s, downward 
C) 12 kg .  m/s, upward 
D) 24 kg .  m/s, downward 
E) 24 kg .  m/s, upward

Question 6

A 0.50-kg bomb is sliding along an icy pond (frictionless surface) with a velocity of 2.0 m/s to the west. The bomb explodes into two pieces. After the explosion, a 0.20-kg piece moves south at 4.0 m/s. What are the components of the velocity of the 0.30-kg piece?

Accepted Answer

A) 4.0 m/s north, 0 m/s 
B) 2.7 m/s north, 3.3 m/s west 
C) 4.0 m/s north, 2.7 m/s west 
D) 0 m/s, 2.0 m/s east 
E) 4.0 m/s north, 2.0 m/s east

Question 7

Two objects of equal mass traveling toward each other with equal speeds undergo a head on collision. Which one of the following statements concerning their velocities after the collision is necessarily true?

Accepted Answer

A) They will exchange velocities. 
B) Their velocities will be reduced. 
C) Their velocities will be unchanged. 
D) Their velocities will be zero. 
E) Their velocities may be zero.

Question 8

An airplane is traveling at 225 m/s when it strikes a weather balloon (m = 1.82 kg), which can be considered to be at rest relative to the ground below. After the collision, the balloon is caught on the fuselage and is traveling with the airplane. The collision takes place over a time interval of 4.44 × 10-3 N. What is the average force that the balloon exerts on the airplane during the collision?

Accepted Answer

A) 415 N 
B) 2.78 × 104 N 
C) 9.22 × 104 N 
D) 4.61 × 105 N 
E) 5.07 × 106 N

Question 9

A 0.2-kg steel ball is dropped straight down onto a hard, horizontal floor and bounces straight up. The ball's speed just before and just after impact with the floor is 10 m/s. Determine the magnitude of the impulse delivered to the floor by the steel ball.

Accepted Answer

A) zero N .  s 
B) 2 N .  s 
C) 4 N .  s 
D) 20 N .  s 
E) 200 N .  s

Question 10

A 2-kg stone falls 100 meters near the surface of the earth. It strikes the ground without any rebound thereby making a completely inelastic collision with the earth. Approximately how much kinetic energy is transferred to the earth in this process?

Accepted Answer

A) zero joules 
B) 200 J 
C) 2000 J 
D) 10 000 J 
E) 20 000 J

Question 11

A 100-kg fisherman and a 500-kg supply crate are on a frozen pond that is essentially frictionless. The man and the crate are initially separated by a distance of 600 meters. The fisherman uses a very light rope to pull the crate closer to him. How far has the man moved when the crate reaches the fisherman?

Accepted Answer

A) zero meters 
B) 10 m 
C) 50 m 
D) 100 m 
E) 500 m

Question 12

A 50-kg toboggan is coasting on level snow. As it passes beneath a bridge, a 20-kg parcel is dropped straight down and lands in the toboggan. If KE1 is the original kinetic energy of the toboggan and KE2 is the kinetic energy after the parcel has been added, what is the ratio KE2/KE1.

Accepted Answer

A) 0.4 
B) 0.6 
C) 0.7 
D) 0.8 
E) 1

Question 13

Complete the following statement: Different types of collisions between interacting bodies are categorized on the basis of

Accepted Answer

A) kinetic energy conservation. 
B) mechanical energy conservation. 
C) linear momentum conservation. 
D) the magnitude of the forces involved. 
E) the temporal duration of the collision.

Question 14

Which one of the following is characteristic of an inelastic collision?

Accepted Answer

A) Total mass is not conserved. 
B) Total energy is not conserved. 
C) Linear momentum is not conserved. 
D) Kinetic energy is not conserved. 
E) The change in momentum is less than the total impulse.

Question 15

Two objects constitute an isolated system. In an elastic collision between the two objects, which one of the following statements is a false statement?

Accepted Answer

A) The total kinetic energy is conserved. 
B) The kinetic energy of each object is the same before and after the collision. 
C) The total momentum is conserved. 
D) The magnitude of the force exerted by each object on the other object is equal. 
E) The total kinetic energy before the collision is equal to the total kinetic energy after the collision.

Question 16

A 35-kg girl is standing near and to the left of a 43-kg boy on the frictionless surface of a frozen pond. The boy throws a 0.75-kg ice ball to the girl with a horizontal speed of 6.2 m/s. What are the velocities of the boy and the girl immediately after the girl catches the ice ball? girl boy

Accepted Answer

A) 0.81 m/s, left 0.67 m/s, right 
B) 0.17 m/s, left 0.14 m/s, left 
C) 0.18 m/s, right 0.13 m/s, left 
D) 0.42 m/s, left 0.49 m/s, right 
E) 0.13 m/s, left 0.11 m/s, right

Question 17

A baseball of mass m, initially at rest, is struck by a bat so that it acquires a speed v. If t represents the duration of the collision between the bat and the ball, which one of the following expressions determines the magnitude of the average force exerted on the ball?

Accepted Answer

A) (1/2)mv2 
B) mv/t 
C) (1/2)mv2t 
D) mt2/(2v) 
E) mvt

Question 18

A 7.30-kg bowling ball strikes a 1.60-kg pin at rest head-on. Before the collision, the velocity of the ball is +6.00 m/s. After the collision, the velocity of the ball is +5.40 m/s. What is the velocity of the pin after the collision?

Accepted Answer

A) +0.6 m/s 
B) +5.4 m/s 
C) +1.2 m/s 
D) +2.7 m/s 
E) +3.2 m/s

Question 19

While in Earth's orbit, an 80-kg astronaut carrying a 20-kg tool kit is initially drifting toward a stationary (relative to her) space shuttle at a speed of 2 m/s. If she throws the tool kit toward the shuttle with a speed of 6 m/s as seen from the shuttle, her final speed is

Accepted Answer

A) 1 m/s toward the shuttle. 
B) 1 m/s away from the shuttle. 
C) 2 m/s toward the shuttle. 
D) 4 m/s toward the shuttle. 
E) 6 m/s away from the shuttle.

Question 20

A sled of mass m is coasting on the icy surface of a frozen river. While it is passing under a bridge, a package of equal mass m is dropped straight down and lands on the sled (without causing any damage). The sled plus the added load then continue along the original line of motion. How does the kinetic energy of the (sled + load) compare with the original kinetic energy of the sled?

Accepted Answer

A) It is 1/4 the original kinetic energy of the sled. 
B) It is 1/2 the original kinetic energy of the sled. 
C) It is 3/4 the original kinetic energy of the sled. 
D) It is the same as the original kinetic energy of the sled. 
E) It is twice the original kinetic energy of the sled.

Exam 7: Impulse and Momentum