A1000 kg red car traveling at 40 m/s rear ends a 3000 kg blue car traveling at 35 m/s. the cars bounce off each other and the blue car is accelerated to 37.5 m/s. what is the velocity of the red car after the crash?

32.5 ms⁻¹

Explanation:

Theory

The law of conservation of linear momentum

The sum of linear momentum of a system under no external force remains constant.

In this scenario although different forces act on two vehicles by each other when we  consider the total system of two cars no external unbalance force act on them. So we can apply this law.

As law says,

The sum of linear momentum before collision = The sum of linear momentum after collision.

Momentum = mass × velocity

1000×40+3000×35 = 1000×v + 3000×37.5

where v = velocity of the red car after the cash

v = 32.5 ms⁻¹

i don't understand. explain it clearly