Question

A 1250 kg car is stopped at a traffic light. A 3550 kg truck moving at 8.33 m/s strikes the car from behind, causing the bumpers to lock together.

A) What is the momentum of the car-truck system before the collision?

B) What is the momentum of the car-truck system after the collision?

C) How fast do the car and truck move after the collision?

(Do NOT put any links or reproductions, I just need help with this.)​

Answer 1

A) Before the collision, the total momentum is

(1250 kg) (0 m/s) + (3550 kg) (8.33 m/s) ≈ 29,600 kg•m/s

B) Momentum is conserved, so after the collision it is still approximately 29,600 kg•m/s.

C) If v is the speed of the locked car-truck system, then

(1250 kg) (0 m/s) + (3550 kg) (8.33 m/s) = (1250 kg + 3550 kg) v

Solve for v :

29,571.5 kg•m/s = (4800 kg) v

v ≈ 6.16 m/s