Question

A moving car of mass 500 kg collides with a stationary truck of

mass 1500 kg, and the two vehicles lock together on impact.
The combined velocity of the car and truck after the collision is
20 m/s. What is the velocity of the car before the collision?

Answer 1

We are given:

m1 = 500 kg m2 = 1500 kg

v1(initial) = x m/s v2(initial) = 0 m/s

v1(final) = 20 m/s v2(final) = 20m/s

According the the law of conservation of momentum:

m1v1(initial) + m2v2(initial) = m1v1(final) + m2v2(final)

Plugging the values in this formula:

(500*x) + (1500 * 0) = (500 * 20) + (1500 * 20)

500x = 20(1500 + 500)

500x = 20(2000)

x = 20 * 4

x = 80 m/s

Therefore, the car was initially moving at a velocity of 80 m/s