Question 1

In a perfectly ELASTIC collision between two perfectly rigid objects

Accepted Answer

A)  the momentum of each object is conserved. 
B)  the kinetic energy of each object is conserved. 
C)  the momentum of the system is conserved but the kinetic energy of the system is not conserved. 
D)  both the momentum and the kinetic energy of the system are conserved. 
E)  the kinetic energy of the system is conserved, but the momentum of the system is not conserved. 
A)  the momentum of each object is conserved. 
B)  the kinetic energy of each object is conserved. 
C)  the momentum of the system is conserved but the kinetic energy of the system is not conserved. 
D)  both the momentum and the kinetic energy of the system are conserved. 
E)  the kinetic energy of the system is conserved, but the momentum of the system is not conserved. D

Question 2

In the figure, a 60-cm length of uniform wire, of 60 g mass and negligible thickness, is bent into a right triangle. The x and y coordinates of the center of mass, in cm, are closest to

Accepted Answer

A)  (8, 3). 
B)  (8, 5). 
C)  (9, 4). 
D)  (10, 3). 
E)  (10, 5). 
A)  (8, 3). 
B)  (8, 5). 
C)  (9, 4). 
D)  (10, 3). 
E)  (10, 5). D

Question 3

A 2.3-kg object traveling at 6.1 m/s collides head-on with a 3.5-kg object traveling in the opposite direction at 4.8 m/s. If the collision is perfectly elastic, what is the final speed of the 2.3-kg object?

Accepted Answer

A)  0.48 m/s 
B)  7.1 m/s 
C)  3.8 m/s 
D)  4.3 m/s 
E)  6.6 m/s 
A)  0.48 m/s 
B)  7.1 m/s 
C)  3.8 m/s 
D)  4.3 m/s 
E)  6.6 m/s B

Question 4

Two automobiles traveling at right angles to each other collide and stick together. Car A has a mass of 1200 kg and had a speed of 25 m/s before the collision. Car B has a mass of 1600 kg. The skid marks show that, immediately after the collision, the wreckage was moving in a direction making an angle of 40° with the original direction of car A. What was the speed of car B before the collision, assuming that any other unbalanced forces are negligible?

Accepted Answer

A)  16 m/s 
B)  18 m/s 
C)  11 m/s 
D)  21 m/s 
E)  14 m/s 
A)  16 m/s 
B)  18 m/s 
C)  11 m/s 
D)  21 m/s 
E)  14 m/s

Question 5

In the figure, four point masses are placed as shown. The x and y coordinates of the center of mass are closest to

Accepted Answer

A)  (2.2 m, 2.6 m). 
B)  (2.2 m, 2.7 m). 
C)  (2.3 m, 2.6 m). 
D)  (2.3 m, 2.7 m). 
E)  (2.3 m, 2.8 m). 
A)  (2.2 m, 2.6 m). 
B)  (2.2 m, 2.7 m). 
C)  (2.3 m, 2.6 m). 
D)  (2.3 m, 2.7 m). 
E)  (2.3 m, 2.8 m).

Question 6

In the figure, determine the character of the collision. The masses of the blocks, and the velocities before and after are given, and no other unbalanced forces act on these blocks. The collision is

Accepted Answer

A)  perfectly elastic. 
B)  partially inelastic. 
C)  completely inelastic. 
D)  characterized by an increase in kinetic energy. 
E)  not possible because momentum is not conserved. 
A)  perfectly elastic. 
B)  partially inelastic. 
C)  completely inelastic. 
D)  characterized by an increase in kinetic energy. 
E)  not possible because momentum is not conserved.

Question 7

A 620-g object traveling at 2.1 m/s collides head-on with a 320-g object traveling in the opposite direction at 3.8 m/s. If the collision is perfectly elastic, what is the change in the kinetic energy of the 620-g object?

Accepted Answer

A)  It loses 0.23 J. 
B)  It gains 0.69 J. 
C)  It loses 0.47 J. 
D)  It loses 1.4 J. 
E)  It doesn't lose any kinetic energy because the collision is elastic. 
A)  It loses 0.23 J. 
B)  It gains 0.69 J. 
C)  It loses 0.47 J. 
D)  It loses 1.4 J. 
E)  It doesn't lose any kinetic energy because the collision is elastic.

Question 8

A 1.2-kg spring-activated toy bomb slides on a smooth surface along the x-axis with a speed of 0.50 m/s. At the origin 0, the bomb explodes into two fragments. Fragment 1 has a mass of 0.40 kg and a speed of 0.90 m/s along the negative y-axis. In the figure, the angle θ, made by the velocity vector of fragment 2 and the x-axis, is closest to

Accepted Answer

A)  31°. 
B)  37°. 
C)  38°. 
D)  53°. 
E)  59°. 
A)  31°. 
B)  37°. 
C)  38°. 
D)  53°. 
E)  59°.

Question 9

Two ice skaters push off against one another starting from a stationary position. The 45.0-kg skater acquires a speed of 0.375 m/s. What speed does the 60.0-kg skater acquire? Assume that any other unbalanced forces during the collision are negligible.

Accepted Answer

A)  0.500 m/s 
B)  0.281 m/s 
C)  0.375 m/s 
D)  0.750 m/s 
E)  0.000 m/s 
A)  0.500 m/s 
B)  0.281 m/s 
C)  0.375 m/s 
D)  0.750 m/s 
E)  0.000 m/s

Question 10

In an INELASTIC collision between two objects

Accepted Answer

A)  the momentum of each object is conserved. 
B)  the kinetic energy of each object is conserved. 
C)  the momentum of the system is conserved but the kinetic energy of the system is not conserved. 
D)  both the momentum and the kinetic energy of the system are conserved. 
E)  the kinetic energy of the system is conserved, but the momentum of the system is not conserved. 
A)  the momentum of each object is conserved. 
B)  the kinetic energy of each object is conserved. 
C)  the momentum of the system is conserved but the kinetic energy of the system is not conserved. 
D)  both the momentum and the kinetic energy of the system are conserved. 
E)  the kinetic energy of the system is conserved, but the momentum of the system is not conserved.

Question 11

There must be equal amounts of mass on both side of the center of mass of an object.

Accepted Answer

A) True 
 B)False

Question 12

A pool player is attempting a fancy shot. He hits the cue ball giving it a speed of 5.57 m/s and directs its center on a path tangent to the surface of the target ball having the same mass as the cue ball. After the collision (on a frictionless table) the initially-stationary ball moves with a speed of 4.82 m/s. After the collision, the new speed of the cue ball and the relative direction of the balls are closest to

Accepted Answer

A)  2.79 m/s, at 90° to each other. 
B)  2.79 m/s, at 60° to each other. 
C)  8.34 m/s, at 90° to each other. 
D)  8.34 m/s, at 60° to each other. 
A)  2.79 m/s, at 90° to each other. 
B)  2.79 m/s, at 60° to each other. 
C)  8.34 m/s, at 90° to each other. 
D)  8.34 m/s, at 60° to each other.

Question 13

You are standing on a skateboard, initially at rest. A friend throws a very heavy ball towards you. You can either catch the object or deflect the object back towards your friend (such that it moves away from you with the same speed as it was originally thrown). What should you do in order to MINIMIZE your speed on the skateboard?

Accepted Answer

A)  Catch the ball. 
B)  Deflect the ball. 
C)  Your final speed on the skateboard will be the same regardless whether you catch the ball or deflect the ball. 
A)  Catch the ball. 
B)  Deflect the ball. 
C)  Your final speed on the skateboard will be the same regardless whether you catch the ball or deflect the ball.

Question 14

A 1.2-kg spring-activated toy bomb slides on a smooth surface along the x-axis with a speed of 0.50 m/s. At the origin 0, the bomb explodes into two fragments. Fragment 1 has a mass of 0.40 kg and a speed of 0.90 m/s along the negative y-axis. In the figure, the energy released by the explosion is closest to

Accepted Answer

A)  0.20 J. 
B)  0.24 J. 
C)  0.28 J. 
D)  0.32 J. 
E)  0.36 J. 
A)  0.20 J. 
B)  0.24 J. 
C)  0.28 J. 
D)  0.32 J. 
E)  0.36 J.

Question 15

A 10.0-kg shell is traveling horizontally to the right at 25.0 m/s relative to the ground when it explodes into two fragments, one of mass 3.00 kg and the other of mass 7.00 kg. The lighter fragment goes directly forward, and the explosion releases 1.50 × 103 J of mechanical energy to the fragments. Find the magnitude and direction of the velocity of the heavier fragment relative to the ground just after the explosion. Ignore the effect of any ejected gases.

Accepted Answer

13.7 m/s t

Question 16

On a smooth horizontal floor, an object slides into a spring which is attached to another mass that is initially stationary. When the spring is most compressed, both objects are moving at the same speed. Ignoring friction, what is conserved during this interaction?

Accepted Answer

A)  momentum and mechanical energy 
B)  momentum only 
C)  kinetic energy only 
D)  momentum and kinetic energy 
E)  momentum and potential energy 
A)  momentum and mechanical energy 
B)  momentum only 
C)  kinetic energy only 
D)  momentum and kinetic energy 
E)  momentum and potential energy

Question 17

A long thin rod of length L has a linear density λ(x) = Ax where x is the distance from the left end of the rod.
(a) How far is the center of mass of the rod from the left end of the rod?
(b) What is the mass of the rod?

Accepted Answer

The answer of A long thin rod of length L...

Question 18

A 15-g bullet is shot vertically into an 2-kg block. The block lifts upward 8.0 mm (see the figure). The bullet penetrates the block and comes to rest in it in a time interval of 0.0010 s. Assume the force on the bullet is constant during penetration and that air resistance is negligible. The initial kinetic energy of the bullet is closest to

Accepted Answer

A)  21 J 
B)  14 J 
C)  10 J 
D)  0.0012 J 
E)  0.16 J 
A)  21 J 
B)  14 J 
C)  10 J 
D)  0.0012 J 
E)  0.16 J

Question 19

A block of mass m = 8.40 kg, moving on a horizontal frictionless surface with a speed 4.20 m/s, makes a perfectly elastic collision with a block of mass M at rest. After the collision, the 8.40 block recoils with a speed of 0.400 m/s. In the figure, the blocks are in contact for 0.200 s. The magnitude of the average force on the 8.40-kg block, while the two blocks are in contact, is closest to

Accepted Answer

A)  193 N 
B)  185 N 
C)  176 N 
D)  168 N 
E)  160 N 
A)  193 N 
B)  185 N 
C)  176 N 
D)  168 N 
E)  160 N

Question 20

A firecracker breaks up into several pieces, one of which has a mass of 200 g and flies off along the x-axis with a speed of 82.0 m/s. A second piece has a mass of 300 g and flies off along the y-axis with a speed of 45.0 m/s. What are the magnitude and direction of the total momentum of these two pieces?

Accepted Answer

A)  361 kg∙m/s at 56.3° from the x-axis 
B)  93.5 kg∙m/s at 28.8° from the x-axis 
C)  21.2 kg∙m/s at 39.5° from the x-axis 
D)  361 kg∙m/s at 0.983° from the x-axis 
E)  21.2 kg∙m/s at 56.3° from the x-axis 
A)  361 kg∙m/s at 56.3° from the x-axis 
B)  93.5 kg∙m/s at 28.8° from the x-axis 
C)  21.2 kg∙m/s at 39.5° from the x-axis 
D)  361 kg∙m/s at 0.983° from the x-axis 
E)  21.2 kg∙m/s at 56.3° from the x-axis

Exam 8: Momentum, Impulse, and Collisions

In a perfectly ELASTIC collision between two perfectly rigid objects

In the figure, a 60-cm length of uniform wire, of 60 g mass and negligible thickness, is bent into a right triangle. The x and y coordinates of the center of mass, in cm, are closest to

A 2.3-kg object traveling at 6.1 m/s collides head-on with a 3.5-kg object traveling in the opposite direction at 4.8 m/s. If the collision is perfectly elastic, what is the final speed of the 2.3-kg object?

In the figure, four point masses are placed as shown. The x and y coordinates of the center of mass are closest to

In the figure, determine the character of the collision. The masses of the blocks, and the velocities before and after are given, and no other unbalanced forces act on these blocks. The collision is

A 620-g object traveling at 2.1 m/s collides head-on with a 320-g object traveling in the opposite direction at 3.8 m/s. If the collision is perfectly elastic, what is the change in the kinetic energy of the 620-g object?

Two ice skaters push off against one another starting from a stationary position. The 45.0-kg skater acquires a speed of 0.375 m/s. What speed does the 60.0-kg skater acquire? Assume that any other unbalanced forces during the collision are negligible.

In an INELASTIC collision between two objects

There must be equal amounts of mass on both side of the center of mass of an object.

On a smooth horizontal floor, an object slides into a spring which is attached to another mass that is initially stationary. When the spring is most compressed, both objects are moving at the same speed. Ignoring friction, what is conserved during this interaction?

A long thin rod of length L has a linear density λ(x) = Ax where x is the distance from the left end of the rod. (a) How far is the center of mass of the rod from the left end of the rod? (b) What is the mass of the rod?

Units, Physical Quantities, and Vectors

Motion Along a Straight Line

Motion in Two or Three Dimensions

Newtons Laws of Motion

Applying Newtons Laws

Work and Kinetic Energy

Potential Energy and Energy Conservation

Rotation of Rigid Bodies

Equilibrium and Elasticity

Fluid Mechanics

Gravitation

Periodic Motion

Mechanical Waves

Sound and Hearing

Temperature and Heat

Thermal Properties of Matter

The First Law of Thermodynamics

The Second Law of Thermodynamics

Electric Charge and Electric Field

Gausss Law

Electric Potential

Capacitance and Dielectrics

Current, Resistance, and Electromotive Force

Direct-Current Circuits

Magnetic Field and Magnetic Forces

Sources of Magnetic Field

Electromagnetic Induction

Inductance

Alternating Current

Electromagnetic Waves

The Nature and Propagation of Light

Geometric Optics

Interference

Diffraction

Relativity

Photons: Light Waves Behaving As Particles

Particles Behaving As Waves

Quantum Mechanics

Atomic Structure

Molecules and Condensed Matter

Nuclear Physics

Particle Physics and Cosmology

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