A 2575 kg van runs into the back of a 825 kg compact car at rest. The move off together at 8.5 m/s. Assuming the friction with the road can be negligible, find the initial speed of the van.

11.2 m/s

Explanation:

The overall momentum of the system is always conserved according to the law of momentum. Momentum of the system after collision is equal to the momentum of the system before collision.

Momentum = mass*velocity;

The momentum of the system after collision = (2575+825) * 8.5 = 28900kg⋅m/s;

The momentum of system before collision = 28900 kg⋅m/s;

28900 = momentum of van + momentum of car

28900 = 2575*v + 825*0

V=11.2 m/s