Physics Question

Question

A demolition derby is a car-crashing contest. Suppose an 800-kg car moving at 20 m/s crashes into the back of and sticks to a 1,200-kg car moving at 10 m/s in the same direction

1. What is the total momentum of the stuck together cars after the collision?
2. What is the speed of the stuck together cars after the collision?

Answer 1

The momentum before and after the collision is the same regardless of how they collide. The initial momentum is 800 kg x 20 m/s + 1200 kg x 10 m/s = 16,000 + 12,000 = 28000 kg m/s.

when they stick together they have a combined mass of 2000 kg. Using conservation of momentum

2000 x velocity = 28000 there fore the final velocity of the two will be 14 m/s