An ore car of mass 4 900 kg rolls downhill on tracks from a mine.At the end of the tracks,13.5 m lower in elevation,is a spring with k = 410 000 N/m.How much is the spring compressed in stopping the ore car? Ignore friction.

Question

Quizplus · Accepted Answer

The potential energy the ore car possessed at the top of the hill would be converted to the potential energy stored in the compressed spring when the car reaches the end of the tracks. 
So, we can use the Law of Conservation of Energy,
mgh = 0.5kx^2
where, h = 13.5m, k = 410000 N/m, m = 4900 kg
Solving for x, we get x = 1.78 m. 
Therefore, the spring compresses by 1.78 m to stop the ore car. 
Hence, the answer is (C).

An Ore Car of Mass 4 900 Kg Rolls Downhill