Question 1

A uniform piece of wire, 20 cm long, is bent in a right angle in the center to give it an L-shape. How far from the bend is the center of mass of the bent wire?

Accepted Answer

A)  2.5 cm 
B)  3.5 cm 
C)  4.5 cm 
D)  5.0 cm 
E)  7.1 cm 
A)  2.5 cm 
B)  3.5 cm 
C)  4.5 cm 
D)  5.0 cm 
E)  7.1 cm

Question 2

A 0.140-kg baseball is dropped from rest from a height of 2.00 m above the ground. What is the magnitude of its momentum just before it hits the ground?

Accepted Answer

A)  0.280 kg∙m/s 
B)  0.877 kg∙m/s 
C)  0.439 kg∙m/s 
D)  0.620 kg∙m/s 
E)  1.37 kg∙m/s 
A)  0.280 kg∙m/s 
B)  0.877 kg∙m/s 
C)  0.439 kg∙m/s 
D)  0.620 kg∙m/s 
E)  1.37 kg∙m/s

Question 3

Define an inelastic collision in terms of conservation of momentum and energy.

Accepted Answer

In an inelastic coll

Question 4

A freight car moves along a frictionless level railroad track at constant speed. The freight car is open on top. A large load of coal is suddenly dumped into the car. What happens to the speed of the freight car?

Accepted Answer

A)  It increases. 
B)  It remains the same. 
C)  It decreases. 
D)  It becomes zero. 
E)  Cannot be determined from the information given. 
A)  It increases. 
B)  It remains the same. 
C)  It decreases. 
D)  It becomes zero. 
E)  Cannot be determined from the information given.

Question 5

A particle that has zero momentum must also have zero kinetic energy.

Accepted Answer

A) True 
 B)False

Question 6

A 600-kg car makes a 90° turn. Its speed before the turn is 21.0 m/s and after the turn it is 24.0 m/s. What is the magnitude of the change in the car's momentum?

Accepted Answer

A)  19.1 × 103 kg∙m/s 
B)  10.2 × 103 kg∙m/s 
C)  9.55 × 103 kg∙m/s 
D)  12.0 × 103 kg∙m/s 
E)  22.2 × 103 kg∙m/s 
A)  19.1 × 103 kg∙m/s 
B)  10.2 × 103 kg∙m/s 
C)  9.55 × 103 kg∙m/s 
D)  12.0 × 103 kg∙m/s 
E)  22.2 × 103 kg∙m/s

Question 7

A 2.0-m rope is lying on a table. You pick up one end and start raising it. How high above the table is the center of mass of the rope when half of the rope has lifted off the table?

Accepted Answer

A)  0.25 m 
B)  0.50 m 
C)  0.75 m 
D)  1.0 m 
E)  1.5 m 
A)  0.25 m 
B)  0.50 m 
C)  0.75 m 
D)  1.0 m 
E)  1.5 m

Question 8

A 3.0-kg object moves to the right at 4.0 m/s. It collides head-on with a 6.0-kg object moving to the left at 2.0 m/s. Which statement is correct?

Accepted Answer

A)  The total momentum both before and after the collision is 24 kg ∙ m/s. 
B)  The total momentum before the collision is 24 kg ∙ m/s, and after the collision is 0 kg ∙ m/s. 
C)  The total momentum before the collision is 0 kg ∙ m/s, and after the collision is 24 kg ∙ m/s. 
D)  The total momentum both before and after the collision is zero. 
E)  None of the above is true. 
A)  The total momentum both before and after the collision is 24 kg ∙ m/s. 
B)  The total momentum before the collision is 24 kg ∙ m/s, and after the collision is 0 kg ∙ m/s. 
C)  The total momentum before the collision is 0 kg ∙ m/s, and after the collision is 24 kg ∙ m/s. 
D)  The total momentum both before and after the collision is zero. 
E)  None of the above is true.

Question 9

A 320-g air track cart traveling at 1.25 m/s collides elastically with a stationary 270-g cart. What is the speed of the 320-g cart after the collision?

Accepted Answer

A)  0.678 m/s 
B)  0.106 m/s 
C)  0.212 m/s 
D)  1.36 m/s 
E)  1.14 m/s 
A)  0.678 m/s 
B)  0.106 m/s 
C)  0.212 m/s 
D)  1.36 m/s 
E)  1.14 m/s

Question 10

Jacques and George meet in the middle of a lake while paddling in their canoes. They come to a complete stop and talk for a while. When they are ready to leave, Jacques pushes George's canoe with a force   to separate the two canoes. What is correct to say about the final momentum and kinetic energy of the system?

Accepted Answer

A)  The final momentum is in the direction of   but the final kinetic energy is zero J. 
B)  The final momentum is in the direction opposite of   but the final kinetic energy is zero J. 
C)  The final momentum is in the direction of   and the final kinetic energy is positive. 
D)  The final momentum is zero kg∙m/s and the final kinetic energy is zero J. 
E)  The final momentum is zero kg∙m/s but the final kinetic energy is positive. 
A)  The final momentum is in the direction of   but the final kinetic energy is zero J. 
B)  The final momentum is in the direction opposite of   but the final kinetic energy is zero J. 
C)  The final momentum is in the direction of   and the final kinetic energy is positive. 
D)  The final momentum is zero kg∙m/s and the final kinetic energy is zero J. 
E)  The final momentum is zero kg∙m/s but the final kinetic energy is positive.

Question 11

State the Conservation of Momentum for a System of Objects

Accepted Answer

Internal forces have absolutel

Question 12

A rocket is fired in a gravity-free environment in deep space. The rocket has an initial mass of 8000 kg and ejects gas with a velocity of 2000 m/s. How much gas must be ejected in the first second to give the rocket an acceleration of 30.0 m/s2?

Accepted Answer

A)  120 kg 
B)  7.50 kg 
C)  15.0 kg 
D)  12.0 kg 
E)  150 kg 
A)  120 kg 
B)  7.50 kg 
C)  15.0 kg 
D)  12.0 kg 
E)  150 kg

Question 13

A novice marksman fires a rifle while holding the butt of the rifle a couple of centimeters away from his shoulder. Explain what happens in terms of the physical principles involved.

Accepted Answer

The initial momentum of the bullet/gun s

Question 14

An 80. kg man is skating Northward and happens to collide with a 20. kg boy who is ice skating toward the East. Immediately after the collision, the man and boy are seen to be moving together at 2.5 m/s in a direction 60 degrees North of East. How fast was the boy moving before the collision?

Accepted Answer

The answer of An 80. kg man is skating Northward...

Question 15

The center of mass of an object does not have to be located within the object.

Accepted Answer

A) True 
 B)False

Question 16

A 0.140-kg baseball is dropped from rest. It has a speed of 1.20 m/s just before it hits the ground. It rebounds with a speed of 1.00 m/s. The ball is in contact with the ground for 0.0140 s. What is the average force exerted by the ground on the ball during that time?

Accepted Answer

A)  2.00 N upwards 
B)  2.00 N downwards 
C)  22.0 N upwards 
D)  22.0 N downwards 
E)  0 N 
A)  2.00 N upwards 
B)  2.00 N downwards 
C)  22.0 N upwards 
D)  22.0 N downwards 
E)  0 N

Question 17

A ping-pong ball moving east at a speed of 4 m/s, collides with a stationary bowling ball. The Ping-Pong ball bounces back to the west, and the bowling ball moves very slowly to the east. Which object experiences the greater magnitude impulse during the collision?

Accepted Answer

A)  Neither; both experienced the same magnitude impulse. 
B)  the Ping-Pong ball 
C)  the bowling ball 
D)  It's impossible to tell since the actual mass values are not given. 
E)  It's impossible to tell since the velocities after the collision are unknown. 
A)  Neither; both experienced the same magnitude impulse. 
B)  the Ping-Pong ball 
C)  the bowling ball 
D)  It's impossible to tell since the actual mass values are not given. 
E)  It's impossible to tell since the velocities after the collision are unknown.

Question 18

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?

Accepted Answer

A)  0.500 m/s 
B)  0.281 m/s 
C)  0.375 m/s 
D)  0.750 m/s 
E)  0 m/s 
A)  0.500 m/s 
B)  0.281 m/s 
C)  0.375 m/s 
D)  0.750 m/s 
E)  0 m/s

Question 19

State the Conservation of Linear Momentum.

Accepted Answer

If the net force act

Question 20

Define an elastic collision in terms of conservation of momentum and energy.

Accepted Answer

In an elastic collis

Exam 9: Linear Momentum and Collisions

A uniform piece of wire, 20 cm long, is bent in a right angle in the center to give it an L-shape. How far from the bend is the center of mass of the bent wire?

A 0.140-kg baseball is dropped from rest from a height of 2.00 m above the ground. What is the magnitude of its momentum just before it hits the ground?

Define an inelastic collision in terms of conservation of momentum and energy.

A freight car moves along a frictionless level railroad track at constant speed. The freight car is open on top. A large load of coal is suddenly dumped into the car. What happens to the speed of the freight car?

A particle that has zero momentum must also have zero kinetic energy.

A 600-kg car makes a 90° turn. Its speed before the turn is 21.0 m/s and after the turn it is 24.0 m/s. What is the magnitude of the change in the car's momentum?

A 2.0-m rope is lying on a table. You pick up one end and start raising it. How high above the table is the center of mass of the rope when half of the rope has lifted off the table?

A 3.0-kg object moves to the right at 4.0 m/s. It collides head-on with a 6.0-kg object moving to the left at 2.0 m/s. Which statement is correct?

A 320-g air track cart traveling at 1.25 m/s collides elastically with a stationary 270-g cart. What is the speed of the 320-g cart after the collision?

State the Conservation of Momentum for a System of Objects

A rocket is fired in a gravity-free environment in deep space. The rocket has an initial mass of 8000 kg and ejects gas with a velocity of 2000 m/s. How much gas must be ejected in the first second to give the rocket an acceleration of 30.0 m/s2?

A novice marksman fires a rifle while holding the butt of the rifle a couple of centimeters away from his shoulder. Explain what happens in terms of the physical principles involved.

An 80. kg man is skating Northward and happens to collide with a 20. kg boy who is ice skating toward the East. Immediately after the collision, the man and boy are seen to be moving together at 2.5 m/s in a direction 60 degrees North of East. How fast was the boy moving before the collision?

The center of mass of an object does not have to be located within the object.

A 0.140-kg baseball is dropped from rest. It has a speed of 1.20 m/s just before it hits the ground. It rebounds with a speed of 1.00 m/s. The ball is in contact with the ground for 0.0140 s. What is the average force exerted by the ground on the ball during that time?

A ping-pong ball moving east at a speed of 4 m/s, collides with a stationary bowling ball. The Ping-Pong ball bounces back to the west, and the bowling ball moves very slowly to the east. Which object experiences the greater magnitude impulse during the collision?

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?

State the Conservation of Linear Momentum.

Define an elastic collision in terms of conservation of momentum and energy.

Introduction to Physics

One-Dimensional Kinematics

Vectors in Physics

Two-Dimensional Kinematics

Newtons Laws of Motion

Applications of Newtons Laws

Work and Kinetic Energy

Potential Energy and Conservation of Energy

Rotational Kinematics and Energy

Rotational Dynamics and Static Equilibrium

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Oscillations About Equilibrium

Waves and Sound

Fluids

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The Laws of Thermodynamics

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Electric Current and Direct-Current Circuits

Magnetism

Magnetic Flux and Faradays Law of Induction

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A rocket is fired in a gravity-free environment in deep space. The rocket has an initial mass of 8000 kg and ejects gas with a velocity of 2000 m/s. How much gas must be ejected in the first second to give the rocket an acceleration of 30.0 m/s²?