General & First-year
Pendulum Lab
T = 2π√(L/g) is the first thing you learn about pendulums — and it's only true for small swings. Release the bob from any angle and watch the real motion (integrated with RK4), add damping, change gravity to the Moon's, and overlay the small-angle 'ghost' to see the large-angle period run measurably slower. The period readout shows exactly how far the textbook formula is off.
2.01 s
Small-angle T
2.07 s
Actual period
+3.1 %
Period lag
The small-angle formula T = 2π√(L/g) ignores amplitude. Release from a big angle and the real period runs slower — turn on the ghost to watch them drift apart.
How to use this simulation
T = 2π√(L/g) is the first thing you learn about pendulums — and it's only true for small swings. Release the bob from any angle and watch the real motion (integrated with RK4), add damping, change gravity to the Moon's, and overlay the small-angle 'ghost' to see the large-angle period run measurably slower. The period readout shows exactly how far the textbook formula is off.
Everything runs in your browser — no sign-up, no download. Change a value and the result updates instantly, so you can build a feel for how each input shapes the outcome. It pairs with Crameleon's practice exams and step sheets when you want to go from intuition to working the problems.