Question

A 1550 kg car with it's engine off starts 100 meters high on hill A. It coasts down hill A then up hill B until it stops at a height of 90 meters. How much thermal energy was generated?

Answer 1

The amount of thermal energy was generated

$$\Delta U=\Delta E_p=mg\Delta h\\ =1550*9.8*(100-90)=151900\:\rm J$$