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How does a pendulum work?
Quick answer
A pendulum works by swinging back and forth under gravity: when you lift it to one side, gravity pulls it back down, and its momentum carries it up the other side. This steady, repeating swing makes it a natural timekeeper.
Step by step
- Lifting the bob to one side gives it stored (potential) energy.
- Gravity pulls it back down, converting that into motion (kinetic energy).
- Momentum carries it up the far side, then the cycle repeats.
- For small swings, the time of each swing depends on its length, not how far it swings.
- Friction and air slowly drain its energy, so real pendulums need a push to keep going.
People also ask
Why does a pendulum keep a steady beat?
For small swings, the time of each swing depends almost only on the pendulum's length, so it ticks at a constant rate — which is why it works in clocks.
What makes a pendulum eventually stop?
Air resistance and friction at the pivot gradually remove its energy, so without a push it slows and stops.
Does a heavier bob swing faster?
No. The swing time depends on length and gravity, not the bob's mass — a heavy and a light pendulum of the same length keep the same beat.
Part of the guide: Everyday Machines →