Question

Let's consider a scenario of a roller coaster ride. As the roller coaster at the top begins to descend, it loses height, which means its potential energy decreases and kinetic energy starts increasing and reaches its maximum value.

By using the above scenario, which statement best compares potential and kinetic energy?

Objects always have more potential energy than kinetic energy.
Kinetic energy increases and potential energy decreases when the velocity of an object increases.
Only potential energy decreases when an object’s height increases.

Answer 1

The second statement is best: "Kinetic energy increases and potential energy decreases when the velocity of an object increases."

Why: kinetic energy depends on speed (KE = 1/2 mv^2), so KE grows as velocity grows. In the roller-coaster example gravitational potential energy (PE = mgh) decreases as the coaster loses height, and that lost PE is converted into KE (neglecting friction), so KE increases while PE decreases.

Notes: (1) The first statement is false — which form of energy is larger depends on the situation. (2) The third statement is incorrect — increasing height increases gravitational potential energy, not decreases.