The Clay Owl
A clay owl hangs on a string of beads inside a ring: a pendulum. Give it a gentle push and it swings to and fro, each swing taking the same time whether it swings far or only a little. The time depends only on how long the string is, not on how heavy the owl is. Twist it and it turns back and forth too: the string winds up and unwinds.
Push the owl gently and count its swings in 10 seconds. Push it harder and count again. Is it different?
Additional Information
A pendulum’s swing takes the same time whether it is big or small (for swings that aren’t too wide). Galileo noticed it watching a lamp swing in a cathedral, and for nearly 300 years the best clocks kept time with pendulums. A longer string swings more slowly: a pendulum four times as long takes twice as long for each swing.