INVESTIGATE • EXPERIMENT • EXPLAIN

Science you can experiment with.

A real-time, interactive 3D lab. Change variables, test predictions and record results — right in your browser.

EXPERIMENT 01 / MOTION & FORCES

The pendulum experiment

LIVE 3D

Preview shown. For interaction, open this lab in Safari, Chrome or Edge as a webpage — not an iPhone file preview.

PHYSICS SIMULATION ACTIVE

↔ Drag to rotate · Scroll / pinch to zoom

YOUR EXPERIMENT

Change the variables

⚗

String length 1.25 m

0.55 m1.80 m

Gravity 9.81 m/s²

Moon-likeHigh gravity

Release angle 25°

5°60°

Damping 0.015 s⁻¹

No dampingMore damping

Predicted period*2.24 s

Simulated period—

ANGLE OVER TIME0.0 s

*Small-angle approximation. At larger release angles, the actual period is slightly longer. The simulation uses the nonlinear pendulum equation.

✎ Experiment notebook0 trials

Predict what happens when you change the string length. Then record your observation.

Your recorded trials will appear here.

iPhone / Android / Windows: This version uses a software 3D renderer that does not need WebGL. On a phone, drag the scene with one finger; use the rotation and zoom buttons. Important: an iPhone Files/ChatGPT attachment preview may show only the static picture because it may block JavaScript. To use the controls reliably on mobile, open the lab as an HTTPS webpage in Safari or Chrome. Physical-device testing and hosting are still outstanding.

01 / ASK

What affects a pendulum's period?

Investigate how string length, gravity and release angle affect the time taken for a complete swing.

02 / OBSERVE

Change one variable

Keep the other variables constant. Record your predicted and measured periods, then compare your trials.

03 / EXPLAIN

Think like a scientist

The period depends mainly on length and gravity. For large angles, the small-angle formula becomes less accurate.