SOLUTION: A car is stopped on a road. Another car hits the car from behind and pushes the stopped car to 20 mph. How fast was the moving car going? The car hit did not Apply brakes.

Question 818258: A car is stopped on a road. Another car hits the car from behind and pushes the stopped car to 20 mph. How fast was the moving car going? The car hit did not Apply brakes.
Answer by KMST(5328) (Show Source): You can put this solution on YOUR website!
That is a physics problem, and you do not have enough information.
You could apply conservation of momentum and conservation of energy if there is no braking.

where
=mass of moving car
= mass of stopped car
= initial speed of moving car
= final speed of moving car after the collision
However, you do not know the masses of the cars.
I do not think it can be solved without further information, but I am going to review my physics course to see if and what additional information would be needed.
Was it a fully inelastic collision, where both cars ended up moving together as one so ?
Or were they bumper cars, and it was a fully elastic collision?
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