Step 1:

Mass of car A is kg.

Mass of car B is kg.

Initial speed of car A is m/sec.

Initial speed of car B is m/sec.

Let the velocities of car A and car B after the collision as .

Law of conservation of mechanical energy:  .

Substitute corresponding values in the formula.

Step 2:

The relative velocity of one particle with respect to the other is reversed by the collision.

Substitute in expression (1).

m/sec.

Velocity of car A  after the collision as  m/sec.

(b)

.

Substitute   in .

m/sec.

Velocity of car A  after the collision as m/sec.

(c)

Momentum of car A before the collision is

Calculate the change in momentum of car A after the collision.

Momentum of car A after the collision is .

Change in momentum of car A after the collision is .

.

Change in momentum of car A after the collision is .

(d)

Momentum of car A before the collision is

Calculate the change in momentum of car B after the collision.

Momentum of car A after the collision is .

Change in momentum of car A after the collision is .

.

Change in momentum of car A after the collision is .