Two Cars, No Bounce

## Question:

A 4500 lb car is traveling to the right at 3 fps when it meets a
3000 lb car moving to the left at 6 fps. If the cars crash head
on and become entangled, what is their common velocity just after
the collision. Assume no brakes were applied during the
collision.

## Answer:

The total momentum before the collision will be equal to the
total momentum after the collision. The momentum of the car
moving to the right is its mass of 4500/32.2 slugs times its
velocity of 3 fps or 419.3 slug fps. The momentum of the car
moving to the left is negative 3000/32.2*6 =
559.0 slug fps. The sum is negative 139.7 slug fps. The
velocity immediately after the collision is the final momentum
divided by the final mass or -139.7 slug fps /
232.9 slugs = 0.6 fps to the left.
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