Question

multiple-choice question
what can you do to change the potential energy of a rock on the top of the mountain to kinetic energy?
add more rocks on top of it
roll down the rock
keep it still on top

Explanation:

Potential energy (PE) of an object at a height depends on its position ($PE = mgh$, where $m$ is mass, $g$ is gravity, $h$ is height). Kinetic energy (KE) depends on motion ($KE=\frac{1}{2}mv^2$, $v$ is velocity). To convert PE to KE, the rock needs to move.

• "Add more rocks" changes total mass/PE but not convert PE to KE of this rock.
• "Roll down the rock" makes it move (increases $v$), so PE (from height) converts to KE (from motion).
• "Keep it still" maintains PE (no motion, so KE remains 0).

Answer:

B. Roll down the rock (assuming the options are labeled as A: add more rocks on top of it, B: Roll down the rock, C: keep it still on top)