a train is sitting still at the top of 990-m mountain. it then coasts down the mountain and back up another mountain that is 520 m high. what is the train's speed at the top of the second hill?

Explanation:

At the top of 520 m high mountain , the train will lose potential energy due to loss of height from 990 m to 520 m and gain kinetic energy .

Loss of height = 990 - 520 = 470 m

Loss of potential energy = m x g x 470 where m is mass of the train .

Gain of kinetic energy = 1/2 m v² where v is velocity of train at the top of 550 m high mountain .

1/2 m v² = m x g x 470

v² = 2 x 9.8 x 470

v = 95.98 m /s

truck y has a greater velocity than truck x.