Question 1

Momentum may be expressed in:

Accepted Answer

A) kg/m 
B) gram.s 
C) N.s 
D) kg/(m.s) 
E) N/s

Question 2

A man is marooned at rest on level frictionless ice.In desperation, he hurls his shoe to the right at 15 m/s.If the man weighs 720 N and the shoe weighs 4.0 N, the man moves to the left at approximately:

Accepted Answer

A) 0 m/s 
B) 2.1 * 10-2 m/s 
C) 8.3 * 10-2 m/s 
D) 15 m/s 
E) 1.1 m/s

Question 3

Two objects, X and Y, are held at rest on a horizontal frictionless surface and a spring is compressed between them.The mass of X is 2/5 times the mass of Y.Immediately after the spring is released, X has a kinetic energy of 50 J and Y has a kinetic energy of:

Accepted Answer

A) 20 J 
B) 8 J 
C) 310 J 
D) 125 J 
E) 50 J

Question 4

The center of mass of a system of particles has a constant velocity if:

Accepted Answer

A) the forces exerted by the particles on each other sum to zero 
B) the external forces acting on particles of the system sum to zero 
C) the velocity of the center of mass is initially zero 
D) the particles are distributed symmetrically around the center of mass 
E) the center of mass is at the geometric center of the system

Question 5

Blocks A and B are moving toward each other along the x axis.A has a mass of 2.0 kg and a velocity of 50 m/s, while B has a mass of 4.0 kg and a velocity of -25 m/s.They suffer an elastic collision and move off along the x axis.The kinetic energy transferred from A to B during the collision is:

Accepted Answer

A) 0 J 
B) 2500 J 
C) 5000 J 
D) 7500 J 
E) 10000 J

Question 6

A large wedge with a mass of 10 kg rests on a horizontal frictionless surface, as shown.A block with a mass of 5.0 kg starts from rest and slides down the inclined surface of the wedge, which is rough.At one instant the vertical component of the block's velocity is 3.0 m/s and the horizontal component is 6.0 m/s.At that instant the velocity of the wedge is:

Accepted Answer

A) 3.0 m/s left 
B) 3.0 m/s, right 
C) 6.0 m/s, right 
D) 6.0 m/s, left 
E) 17 m/s, right

Question 7

A golf ball of mass m is hit by a golf club so that the ball leaves the tee with speed v.The club is in contact with the ball for time T.The average force on the club on the ball during the time T is:

Accepted Answer

A) mvT 
B) mv/T 
C) (1/2)mv2T 
D) mv2/(2T) 
E) mT2/(2v)

Question 8

A light rope passes over a light frictionless pulley attached to the ceiling.An object with a large mass is tied to one end and an object with a smaller mass is tied to the other end.Starting from rest, the heavier object moves downward, and the lighter object moves upward with an acceleration of the same magnitude.Which of the following statements is true for the system consisting of the two objects?

Accepted Answer

A) The center of mass remains at rest. 
B) The net external force is zero. 
C) The velocity of the center of mass is a constant. 
D) The acceleration of the center of mass is g, downward. 
E) None of the above statements are true.

Question 9

At one instant of time a rocket is traveling in outer space at 2500 m/s and is exhausting fuel at a rate of 100 kg/s.If the speed of the fuel as it leaves the rocket is 1500 m/s, relative to the rocket, the thrust is:

Accepted Answer

A) 0 N 
B) 1.0 *105 N 
C) 1.5 * 105 N 
D) 2.9 * 105 N 
E) 2.5 * 105 N

Question 10

The center of mass of a system of particles remains at the same place if:

Accepted Answer

A) it is initially at rest and the external forces sum to zero 
B) it is initially at rest and the internal forces sum to zero 
C) the sum of the external forces is less than the maximum force of static friction 
D) no friction acts internally 
E) none of the above

Question 11

At the same instant that a 0.50-kg ball is dropped from 25 m above Earth, a second ball, with a mass of 0.25 kg, is thrown straight upward from Earth's surface with an initial speed of 15 m/s.They move along nearby lines and pass each other without colliding.At the end of 2.0 s the height above Earth's surface of the center of mass of the two-ball system is:

Accepted Answer

A) 2.9 m 
B) 4.0 m 
C) 7.1 m 
D) 7.9 m 
E) 10.4 m

Question 12

In a one-dimensional collision,

Accepted Answer

A) a moving object strikes a stationary object, after which the objects move in arbitrary directions. 
B) the objects must be moving along the same line before the collision, but may be moving in arbitrary directions after the collision. 
C) one of the objects must remain at rest after the collision. 
D) one of the objects must be at rest before the collision. 
E) all motion, both before and after the collision, must be along the same line.

Question 13

Force:

Accepted Answer

A) equals the negative integral (with respect to distance)of the potential energy function 
B) is the ability to do work 
C) is the rate of change of doing work 
D) equals the time rate of change of momentum 
E) has dimensions of momentum multiplied by time

Question 14

A 4.0-N puck is traveling at 3.0 m/s.It strikes an 8.0-N puck, which is stationary.The two pucks stick together.Their common final speed is:

Accepted Answer

A) 1.0 m/s 
B) 1.5 m/s 
C) 2.0 m/s 
D) 2.3 m/s 
E) 3.0 m/s

Question 15

A 3.0-kg cart and a 2.0-kg cart approach each other on a horizontal air track.They collide and stick together.After the collision their total kinetic energy is 40 J.The speed of their center of mass is:

Accepted Answer

A) 0 m/s 
B) 2.8 m/s 
C) 4.0 m/s 
D) 5.2 m/s 
E) 8.0 m/s

Question 16

A 25-kg box of books is dropped on the floor from a height of 1.1 m and comes to rest.What impulse did the floor exert on the box?

Accepted Answer

A) cannot be answered without knowing how long it took the box to stop 
B) 22 kg∙m/s 
C) 120 kg∙m/s 
D) 270 kg∙m/s 
E) 540 kg∙m/s

Question 17

A 2.0-kg mass is attached to one end of a spring with a spring constant of 100 N/m and a 4.0-kg mass is attached to the other end.The masses are placed on a horizontal surface and the spring is compressed 10 cm.The spring is then released with the masses at rest and the masses oscillate.When the spring has its equilibrium length for the first time the 2.0-kg mass has a speed of 0.36 m/s.The mechanical energy that has been lost to this instant is:

Accepted Answer

A) 0 J 
B) 0.31 J 
C) 0.61 J 
D) 0.81 J 
E) 1.2 J

Question 18

Sphere A has mass m and is moving with velocity v.It makes a head-on elastic collision with a stationary sphere B of mass 2m.After the collision their speeds (vA, vB)are:

Accepted Answer

A) 0, v/2 
B) -v/3, 2v/3 
C) -v, v 
D) -2v/3, v/3 
E) none of these

Exam 9: Center of Mass and Linear Momentum

Momentum may be expressed in:

A man is marooned at rest on level frictionless ice.In desperation, he hurls his shoe to the right at 15 m/s.If the man weighs 720 N and the shoe weighs 4.0 N, the man moves to the left at approximately:

Two objects, X and Y, are held at rest on a horizontal frictionless surface and a spring is compressed between them.The mass of X is 2/5 times the mass of Y.Immediately after the spring is released, X has a kinetic energy of 50 J and Y has a kinetic energy of:

The center of mass of a system of particles has a constant velocity if:

Blocks A and B are moving toward each other along the x axis.A has a mass of 2.0 kg and a velocity of 50 m/s, while B has a mass of 4.0 kg and a velocity of -25 m/s.They suffer an elastic collision and move off along the x axis.The kinetic energy transferred from A to B during the collision is:

A golf ball of mass m is hit by a golf club so that the ball leaves the tee with speed v.The club is in contact with the ball for time T.The average force on the club on the ball during the time T is:

At one instant of time a rocket is traveling in outer space at 2500 m/s and is exhausting fuel at a rate of 100 kg/s.If the speed of the fuel as it leaves the rocket is 1500 m/s, relative to the rocket, the thrust is:

The center of mass of a system of particles remains at the same place if:

In a one-dimensional collision,

Force:

A 4.0-N puck is traveling at 3.0 m/s.It strikes an 8.0-N puck, which is stationary.The two pucks stick together.Their common final speed is:

A 3.0-kg cart and a 2.0-kg cart approach each other on a horizontal air track.They collide and stick together.After the collision their total kinetic energy is 40 J.The speed of their center of mass is:

A 25-kg box of books is dropped on the floor from a height of 1.1 m and comes to rest.What impulse did the floor exert on the box?

Sphere A has mass m and is moving with velocity v.It makes a head-on elastic collision with a stationary sphere B of mass 2m.After the collision their speeds (v_A, v_B) are:

Exam 9: Center of Mass and Linear Momentum

Momentum may be expressed in:

A man is marooned at rest on level frictionless ice.In desperation, he hurls his shoe to the right at 15 m/s.If the man weighs 720 N and the shoe weighs 4.0 N, the man moves to the left at approximately:

Two objects, X and Y, are held at rest on a horizontal frictionless surface and a spring is compressed between them.The mass of X is 2/5 times the mass of Y.Immediately after the spring is released, X has a kinetic energy of 50 J and Y has a kinetic energy of:

The center of mass of a system of particles has a constant velocity if:

Blocks A and B are moving toward each other along the x axis.A has a mass of 2.0 kg and a velocity of 50 m/s, while B has a mass of 4.0 kg and a velocity of -25 m/s.They suffer an elastic collision and move off along the x axis.The kinetic energy transferred from A to B during the collision is:

A golf ball of mass m is hit by a golf club so that the ball leaves the tee with speed v.The club is in contact with the ball for time T.The average force on the club on the ball during the time T is:

At one instant of time a rocket is traveling in outer space at 2500 m/s and is exhausting fuel at a rate of 100 kg/s.If the speed of the fuel as it leaves the rocket is 1500 m/s, relative to the rocket, the thrust is:

The center of mass of a system of particles remains at the same place if:

In a one-dimensional collision,

Force:

A 4.0-N puck is traveling at 3.0 m/s.It strikes an 8.0-N puck, which is stationary.The two pucks stick together.Their common final speed is:

A 3.0-kg cart and a 2.0-kg cart approach each other on a horizontal air track.They collide and stick together.After the collision their total kinetic energy is 40 J.The speed of their center of mass is:

A 25-kg box of books is dropped on the floor from a height of 1.1 m and comes to rest.What impulse did the floor exert on the box?

Sphere A has mass m and is moving with velocity v.It makes a head-on elastic collision with a stationary sphere B of mass 2m.After the collision their speeds (vA, vB) are:

Sphere A has mass m and is moving with velocity v.It makes a head-on elastic collision with a stationary sphere B of mass 2m.After the collision their speeds (v_A, v_B) are: