A 150-kg roller-coaster car climbs to the top of a 91 - m - high hill. How much work is done against gravity as the car is lifted to the top of the hill?

10 m/s

Explanation:

The potential energy of the roller coaster is converted to kinetic energy. According to law of transformation of energy, potential energy = kinetic energy.

mgh = ½mv². Take g as 10m/s².

150 * 10 * 50 = ½ * 150 * v².

7500 = 75v².

v² = 7500/75.

v = √100.

v = 10 m/s