Question

You drop the pendulum bob and it swings from point A to point C, and then back again. Eventually it slows down and stops, settling at point B. A similar pendulum can be found in a pendulum clock. However, the clock pendulum does not stop; it continues to swing back and forth, with a tick-tick. Why is there a difference between the lab pendulum and the clock pendulum?
A) All of the potential energy is not converted to kinetic energy.
B) An enclosed pendulum is not acted on by air resistance or gravity.
C) An external energy source, like a battery, is needed to maintain motion.
Eliminate
D) Air resistance is not a factor since the pendulum is housed inside the clock.

Answer 1

B An enclosed pendulum is not acted on by air resistence or gravity. Plus, pendulum's in clocks are electronic (I think) so that's why it keeps moving back in forth. (at least i think so)