Question

A bird flies off of a cliff, dropping a feather and knocking rocks off the cliff. The rocks reach the ground much faster than the feather.

Which energy transformations occur in this case? Check all that apply.

All of the rocks’ potential energy is converted into kinetic energy because rocks do not experience wind resistance.
Some of the potential energy of the feather is converted into kinetic energy.
All of the feather’s potential energy is converted into thermal energy due to the friction of air resistance.
Some of the rocks’ potential energy is converted into thermal energy due to the friction of air resistance.
Some of the feather’s potential energy is converted into thermal energy due to the friction of air resistanc

Answer 1

Correct choices:
- Some of the potential energy of the feather is converted into kinetic energy.
- Some of the rocks’ potential energy is converted into thermal energy due to the friction of air resistance.
- Some of the feather’s potential energy is converted into thermal energy due to the friction of air resistance.

Why: As both objects fall, gravitational potential energy is partly converted to kinetic energy. Air resistance (especially large for the feather) converts a portion of the lost potential energy into thermal energy. The rock’s air resistance is small but nonzero, so not all its PE becomes KE; the feather loses a much larger fraction of its PE to thermal dissipation.