Gears, coaxial discs and pulleys

Connections between rotating discs are everywhere: bicycle gears, transmissions, clocks. There are three fundamental types of connection — rim contact, common axle, belt — each with its own rule relating angular velocity $\omega$ and tangential velocity $v = \omega r$. The key is to keep an eye on the sign of $\omega$.

• Angular velocity and sign convention
• Discs in contact: gears
• Coaxial discs
• Discs connected by a belt
• Summary table of the three cases

Try it — interactive simulation