Two Cars, No Bounce


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.


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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