Question

Olivia is on a swing at the playground.

A girl is swinging on a swing set. At W she is about 45 degrees up and to the left. At X she is near the bottom of the swing just to the left. At Y she is near the bottom of the swing just to the right. At Z she is about 45 degrees up and to the right.
If the swing is moving from W to Z, at which point is her kinetic energy increasing and her potential energy decreasing? (based on a starting point of W)

W
X

Answer 1

X.

Starting at W she’s descending, so gravitational potential energy is being converted into kinetic energy. Throughout the descent (from W toward the lowest point) KE increases and PE decreases — X is on that descent, whereas W is the starting high point where KE is (nearly) zero.