Question 1

The law of conservation of momentum applies to a system of colliding objects only if:

Accepted Answer

A) there is no change in kinetic energy of the system 
B) the coefficient of restitution is one 
C) the coefficient of restitution is zero 
D) the net external impulse is zero 
E) the collisions are all elastic

Question 2

For a two-body collision, involving objects with different masses, a frame of reference which has the same velocity relative to the laboratory as does the center of mass of the two objects is:

Accepted Answer

A) a frame for which the momentum of the incident object is zero 
B) a frame for which the momentum of the target object is zero 
C) a frame for which the average momentum of the two objects is zero 
D) a frame for which the total momentum of the two objects is zero 
E) none of the above

Question 3

A hockey puck of mass m traveling along the x axis at 4.5 m/s hits another identical hockey puck at rest.If after the collision the second puck travels at a speed of 3.5 m/s at an angle of 30° above the x axis, is this an elastic collision?

Accepted Answer

A) Yes, since momentum is conserved. 
B) No, since momentum is not conserved. 
C) Yes, since kinetic energy is conserved. 
D) No, since kinetic energy is not conserved. 
E) Not enough information.

Question 4

When a particle suffers a head-on elastic collision with another particle, initially at rest, the greatest fraction of kinetic energy is transferred if:

Accepted Answer

A) the incident particle is initially traveling very fast 
B) the incident particle is traveling very slowly 
C) the incident particle is much more massive than the target particle 
D) the incident particle is much less massive than the target particle 
E) the incident and target particle have the same mass

Question 5

A stream of gas consists of n molecules.Each molecule has mass m and speed v.The stream is reflected elastically from a rigid surface as shown.The magnitude of the change in the total momentum of the stream is:

Accepted Answer

A) 2mnv 
B) 2mnv sin 30 $\degree$ 
C) mnv sin 30 $\degree$ 
D) mnv cos 30 $\degree$ 
E) mnv

Question 6

Momentum may be expressed in:

Accepted Answer

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

Question 7

The force on a particle is given by F(t)= 0.71 t + 1.2 t2, in N.If the force acts from t = 0 to t = 2.0 s, the total impulse is:

Accepted Answer

A) 1.2 kg∙m/s 
B) 1.9 kg∙m/s 
C) 4.6 kg∙m/s 
D) 4.8 kg∙m/s 
E) 6.2 kg∙m/s

Question 8

If a projectile hits a stationary target, and the projectile rebounds and travels back the way it came,

Accepted Answer

A) the mass of the projectile is much less than the mass of the target. 
B) the mass of the projectile is equal to the mass of the target. 
C) the mass of the projectile is much greater than the mass of the target. 
D) nothing can be said about the masses of the projectile and target without further information. 
E) this is an unphysical situation and will not actually happen.

Question 9

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 10

The direction of the impulse on a struck baseball

Accepted Answer

A) depends on how fast the ball was thrown 
B) is in the direction of the ball's change in velocity 
C) is in the direction of the force of gravity 
D) depends on how hard the ball is struck 
E) Impulse is a scalar, and does not have a direction associated with it.

Question 11

If a projectile hits a stationary target, and the projectile continues to travel in the same direction,

Accepted Answer

A) the mass of the projectile is less than the mass of the target. 
B) the mass of the projectile is equal to the mass of the target. 
C) the mass of the projectile is greater than the mass of the target. 
D) nothing can be said about the masses of the projectile and target without further information. 
E) this is an unphysical situation and will not actually happen.

Question 12

A rifle of mass M is initially at rest but free to recoil.It fires a bullet of mass m and velocity v (relative to the ground).After firing, the velocity of the rifle (relative to the ground)is:

Accepted Answer

A) -mv 
B) -Mv/m 
C) -mv/M 
D) -v 
E) mv/M

Question 13

The velocity of the center of mass of a system of particles changes as v = 4.5 t + 2.4 t2 + 1.1 t3, where v is in meters per second.If the system starts from rest at t = 0, what is its acceleration at t = 3.0 s?

Accepted Answer

A) 7.1 m/s2 
B) 14 m/s2 
C) 20 m/s2 
D) 49 m/s2 
E) 65 m/s2

Question 14

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 15

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 16

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 17

A 1000-kg space probe is motionless in space.To start moving, its main engine is fired for 5 s during which time it ejects exhaust gases at 5000 m/s.At the end of this process it is moving at 20 m/s.The approximate mass of the ejected gas is:

Accepted Answer

A) 0.8 kg 
B) 4 kg 
C) 5 kg 
D) 20 kg 
E) 25 kg

Question 18

The physical quantity "impulse" has the same dimensions as that of:

Accepted Answer

A) force 
B) power 
C) energy 
D) momentum 
E) work

Question 19

The center of mass of a system of particles obeys an equation similar to Newton's second law  where:

Accepted Answer

A)   is the total internal force and m is the total mass of the system 
B)   is the total internal force and m is the mass acting on the system 
C)   is the total external force and m is the total mass of the system 
D)   is the force of gravity and m is the mass of Earth 
E)   is the force of gravity and m is the total mass of the system

Question 20

The center of mass of the system consisting of Earth, the Sun, and the planet Mars is:

Accepted Answer

A) closer to the Earth than to either of the other bodies 
B) closer to the Sun than to either of the other bodies 
C) closer to Mars than to either of the other bodies 
D) at the geometric center of the triangle formed by the three bodies 
E) at the center of the line joining the Earth and Mars

Exam 9: Center of Mass and Linear Momentum

The law of conservation of momentum applies to a system of colliding objects only if:

For a two-body collision, involving objects with different masses, a frame of reference which has the same velocity relative to the laboratory as does the center of mass of the two objects is:

A hockey puck of mass m traveling along the x axis at 4.5 m/s hits another identical hockey puck at rest.If after the collision the second puck travels at a speed of 3.5 m/s at an angle of 30° above the x axis, is this an elastic collision?

When a particle suffers a head-on elastic collision with another particle, initially at rest, the greatest fraction of kinetic energy is transferred if:

Momentum may be expressed in:

The force on a particle is given by F(t) = 0.71 t + 1.2 t², in N.If the force acts from t = 0 to t = 2.0 s, the total impulse is:

If a projectile hits a stationary target, and the projectile rebounds and travels back the way it came,

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

The direction of the impulse on a struck baseball

If a projectile hits a stationary target, and the projectile continues to travel in the same direction,

A rifle of mass M is initially at rest but free to recoil.It fires a bullet of mass m and velocity v (relative to the ground) .After firing, the velocity of the rifle (relative to the ground) is:

The velocity of the center of mass of a system of particles changes as v = 4.5 t + 2.4 t² + 1.1 t³, where v is in meters per second.If the system starts from rest at t = 0, what is its acceleration at t = 3.0 s?

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:

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:

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 1000-kg space probe is motionless in space.To start moving, its main engine is fired for 5 s during which time it ejects exhaust gases at 5000 m/s.At the end of this process it is moving at 20 m/s.The approximate mass of the ejected gas is:

The physical quantity "impulse" has the same dimensions as that of:

The center of mass of a system of particles obeys an equation similar to Newton's second law where:

The center of mass of the system consisting of Earth, the Sun, and the planet Mars is:

Exam 9: Center of Mass and Linear Momentum

The law of conservation of momentum applies to a system of colliding objects only if:

For a two-body collision, involving objects with different masses, a frame of reference which has the same velocity relative to the laboratory as does the center of mass of the two objects is:

A hockey puck of mass m traveling along the x axis at 4.5 m/s hits another identical hockey puck at rest.If after the collision the second puck travels at a speed of 3.5 m/s at an angle of 30° above the x axis, is this an elastic collision?

When a particle suffers a head-on elastic collision with another particle, initially at rest, the greatest fraction of kinetic energy is transferred if:

A stream of gas consists of n molecules.Each molecule has mass m and speed v.The stream is reflected elastically from a rigid surface as shown.The magnitude of the change in the total momentum of the stream is:

Momentum may be expressed in:

The force on a particle is given by F(t) = 0.71 t + 1.2 t2, in N.If the force acts from t = 0 to t = 2.0 s, the total impulse is:

If a projectile hits a stationary target, and the projectile rebounds and travels back the way it came,

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

The direction of the impulse on a struck baseball

If a projectile hits a stationary target, and the projectile continues to travel in the same direction,

A rifle of mass M is initially at rest but free to recoil.It fires a bullet of mass m and velocity v (relative to the ground) .After firing, the velocity of the rifle (relative to the ground) is:

The velocity of the center of mass of a system of particles changes as v = 4.5 t + 2.4 t2 + 1.1 t3, where v is in meters per second.If the system starts from rest at t = 0, what is its acceleration at t = 3.0 s?

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:

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:

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 1000-kg space probe is motionless in space.To start moving, its main engine is fired for 5 s during which time it ejects exhaust gases at 5000 m/s.At the end of this process it is moving at 20 m/s.The approximate mass of the ejected gas is:

The physical quantity "impulse" has the same dimensions as that of:

The center of mass of a system of particles obeys an equation similar to Newton's second law where:

The center of mass of the system consisting of Earth, the Sun, and the planet Mars is:

The force on a particle is given by F(t) = 0.71 t + 1.2 t², in N.If the force acts from t = 0 to t = 2.0 s, the total impulse is:

The velocity of the center of mass of a system of particles changes as v = 4.5 t + 2.4 t² + 1.1 t³, where v is in meters per second.If the system starts from rest at t = 0, what is its acceleration at t = 3.0 s?