Connected Bodies: Pulleys & Blocks Simulation

When bodies are joined by a light string or pushed together, they move with one acceleration. The quick method: treat the whole system as one body to get a = (net external force)/(total mass), then look at one body on its own to find the internal force — the tension or the contact force — that gives it that acceleration.

This connected bodies simulation solves five set-ups that cover most laws-of-motion problems: blocks in contact, blocks joined by a string, the Atwood machine, a block on a table pulled by a hanging mass, and one block stacked on another. Each body carries its own force arrows (its free-body diagram), and the readouts give the acceleration, tension, contact force and friction, with the conditions for motion or slipping.