Two identical cars, P and Q, start at the same level. Car P moves at a constant speed of 10m/s up a hill to a height of 25m in a time of 20s. In the same time car Q moves at a constant speed of 20m/s up a hill to a height of 50m. What are the kinetic energies of the cars while they are travelling up the hills, and what are their gravitational potential energies once they have reached the top?

Answer:

3) C

Formula for kinetic energy = ½mv²
Let mass of P and Q be ‘m’
KE of P = ½m10² = 50m J
KE of Q = ½m20² = 200m J

So, KE of Q is four times P
The squared in the KE formula makes it four times.

Then the height of Q will be twice of P.
So GPE of Q would be twice as much as P.
This corresponds to option C.