Question 1

The impulse delivered to an object is equal to the change in the object's velocity.

Accepted Answer

Impulse is equal to the change in momentum of an object, not just the change in velocity. Momentum is the product of mass and velocity, so impulse is equal to the change in mass times velocity.

Question 2

Internal forces cannot change the total kinetic energy of a system.

Accepted Answer

Internal forces can change the distribution of kinetic energy within a system, but they cannot change the total mechanical energy unless external forces or non-conservative forces (like friction) are involved.

Question 3

Two objects of equal mass are traveling with identical speeds v and collide. After the collision they travel together with a speed v/2. What was the angle between the original velocities?

Accepted Answer

120°

Question 4

When a gun is fired, which has the greater kinetic energy:
 the bullet or the recoiling gun?

Accepted Answer

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Question 5

State Newton's second law in terms of momentum.

Accepted Answer

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Question 6

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

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Question 7

In space there is nothing for the rocket to "push against" so how does it accelerate?

Accepted Answer

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Question 8

State the Conservation of Linear Momentum.

Accepted Answer

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Question 9

When a ball undergoes a one-dimensional elastic collision with a wall, the velocity of the ball is reversed, while the wall remains stationary. Explain why this does not violate conservation of momentum.

Accepted Answer

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Question 10

The net force acting on an object is equal to the rate of change of its momentum.

Accepted Answer

This statement is known as the law of momentum conservation, which states that the total momentum of a system remains constant unless acted upon by an external force. If an external force does act on a system, the change in momentum of the system is directly proportional to the force applied. Therefore, the net force acting on an object is equal to the rate of change of its momentum.

Question 11

An air track cart with mass m and speed v moving along an air track collides with a stationary cart with a mass m/3. After the collision the first cart has a speed v/2. Is the collision elastic?

Accepted Answer

The answer of An air track cart with mass m...

Question 12

An air track cart with mass m and speed v moving along an air track collides with a stationary cart with a mass m/3. After the collision the first cart has a speed v/2. What is the speed of the second cart?

Accepted Answer

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Question 13

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

Accepted Answer

Kinetic energy is defined as 1/2mv^2, where m is the mass and v is the velocity of the particle. Since momentum is defined as p = mv (where p is the momentum), if the particle has zero momentum (p=0), then its velocity (v) must also be zero. Therefore, its kinetic energy (1/2mv^2) would be zero. Hence, a particle that has zero momentum must also have zero kinetic energy.

Question 14

Two objects approach each other with velocities such that the total momentum of the masses is zero kg∙m/s, and undergo an elastic collision. Is the sum of the kinetic energies of each object the same before and after the collision?

Accepted Answer

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Question 15

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

Accepted Answer

A system can have zero momentum if the velocities of its components are equal and opposite, but it can still have kinetic energy due to the motion of its individual components.

Question 16

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

Accepted Answer

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Question 17

In the two-dimensional elastic collision of a particle with a stationary particle that has the same mass, the trajectories of the two particles after the collision are at right angles to each other. Explain why this should be so.

Accepted Answer

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Question 18

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

Accepted Answer

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Question 19

State the Conservation of Momentum for a System of Objects

Accepted Answer

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Question 20

Internal forces cannot change the total momentum of a system.

Accepted Answer

This is a statement of the law of conservation of momentum, which states that the total momentum of a system remains constant in the absence of external forces. Internal forces, which are forces between objects within the system, can transfer momentum between the objects, but they cannot change the total momentum of the system.

Quiz 9: Linear Momentum and Collisions