Question

a rock is thrown straight up from the surface of the earth. which one of the following statements describes the energy transformation of the rock as it rises? neglect air resistance. a. the kinetic energy increases and the potential energy decreases. b. both the kinetic energy and the potential energy of the rock remain the same. c. the total energy of the rock increases. d. the kinetic energy decreases and the potential energy increases. e. both the potential energy and the total energy of the rock increase.

Explanation:

Step1: Recall energy - conservation and formulas

Kinetic energy $K=\frac{1}{2}mv^{2}$ and gravitational potential energy $U = mgh$. As the rock rises, its velocity $v$ decreases (because of the gravitational acceleration acting down - ward), so $K$ decreases. And its height $h$ increases, so $U$ increases.

Step2: Consider total energy

Since there is no air - resistance (no non - conservative force), the total mechanical energy $E=K + U$ is conserved.

Answer:

D. The kinetic energy decreases and the potential energy increases.