Atwood Machine

Dynamics

Two masses connected by a string over a pulley demonstrating Newton's second law — adjust the masses to see how the weight difference drives acceleration.

How this simulation works

Use the Mass 1 and Mass 2 sliders to set the weight of each hanging mass in kilograms. Press Start to release the system — the heavier mass descends while the lighter one rises, connected by a string over the pulley. Press Pause to freeze the motion mid-run and Resume to continue. Press Reset to return both masses to their starting positions. Try setting the masses equal to see the system stay still, then increase one mass to watch the acceleration grow. The readouts show elapsed time, the system's current speed, and the theoretical acceleration.