pendulum

Everyday

1. A pendulum is a weight hanging from a fixed point on a string or rod, which swings backwards and forwards. tree →
2. The swinging part of some old clocks, like a grandfather clock, which keeps the clock on time. tree →
3. The idea of something changing from one extreme to the other and back again, like the «pendulum of opinion». tree →

In the lessons

In science lessons pupils make a pendulum with string and a weight, time its swings with a stopwatch and find that the length of the string changes how long one swing takes, while the weight hardly does; it is a classic fair test. In stories a ticking pendulum clock adds a spooky or calm feeling. Phrases: swing like a pendulum, the pendulum swings, pendulum clock, the pendulum of a clock.

Examples

• The pendulum of the grandfather clock swung slowly. tree →
• We timed ten swings of the pendulum and divided by ten. tree →
• A longer pendulum swings more slowly. tree →
• Changing the weight did not change the pendulum's time much. tree →
• Galileo noticed a lamp swinging like a pendulum in a church. tree →
• The hypnotist swung a watch like a pendulum. tree →
• The pendulum of fashion has swung back to wide trousers. tree →
• A playground swing is a kind of pendulum. tree →
• The pendulum of the great clock went to and fro, and the hands turned, and everything in the room became still older; but they did not observe it. tree →

Note

Countable: one pendulum, two pendulums (the Latin plural «pendula» is very rare). Pronounced «PEN-dyoo-lum» or «PEN-juh-lum». In science investigations: to measure the time of one swing more accurately, time ten swings and divide by 10. Trap: many children guess a heavier weight swings faster, but the length of the string matters, not the weight.