In a trial, an expert witness uses the conservation of momentum to demonstrate which initial velocities would give the final states that occurred in the accident. Can using the conservation of momentum be justified in this case?

Question

Question 5 options:

Yes, because momentum is conserved in all collisions.

No, momentum is only conserved in elastic collisions which this is not.

No, energy is always conserved, but momentum is only sometimes conserved.

Yes, because momentum is conserved in inelastic collisions which all car accidents are.

Question 6 (5 points)
Which factors below will increase the momentum of a rolling ball of constant mass m? (Select only the answers that will increase the momentum of the ball.)




Question 6 options:

Rolling uphill onto an inclined surface.

Colliding with a ball of much lower mass moving in the opposite direction of the ball.

Rolling onto a surface with high amounts of friction with the ball.

Moving from a flat surface to moving downhill.

A moving object traveling in the same direction as the ball colliding with it.

Answer 1

Question 5

The appropriate option to answer whether using the conservation of momentum can be justified in the trial case is:

Yes, because momentum is conserved in inelastic collisions which all car accidents are.

This is correct because momentum is always conserved in isolated systems, which includes both elastic and inelastic collisions. While kinetic energy is only conserved in elastic collisions, momentum will be conserved even in inelastic collisions such as car accidents.

Question 6

The factors that will increase the momentum of a rolling ball of constant mass \(m\) are:

• Moving from a flat surface to moving downhill.
  This will increase the velocity of the ball, and since momentum \(p = mv\), if the velocity increases, the momentum increases.

• A moving object traveling in the same direction as the ball colliding with it.
  If the moving object is moving in the same direction and collides with the ball, it can transfer additional momentum to the ball, thus increasing its momentum.

The other options either do not increase the ball's velocity or would likely reduce momentum due to energy losses (like friction or an uphill roll).