Pendulum: what sets the period

What the experiment shows

Two identical balls hang on rods of different lengths and are released from the same angle. The short pendulum swings faster.

How to run it

1. Press “Run” and count each pendulum’s swings in 10 seconds.
2. Write the results down and compare: how many times do the lengths differ, and how many times the swing counts?
3. In the editor set a ball’s mass to 5 — did the period change?

Questions to discuss

• Why does a long pendulum in old clocks tick more slowly?
• How should the length change to make the period twice as long?

The science

A pendulum’s period T = 2π·√(L/g) depends on length L and gravity g, not on the ball’s mass. To double the period, make the length four times larger.

Try it at home

Tie a nut to a thread: one 25 cm long, another 100 cm. Swing them and count the swings in 20 seconds. The longer thread makes half as many swings.

What to change in the editor

• Increase the starting angle — the period barely changes while the angle is small.
• Set gravity to 1.6 (Moon) — the pendulum slows down.