Friction

Static vs. kinetic

An interactive lesson with 7 steps, about 6 minutes: you predict, drag and solve, with instant feedback on every answer. It runs in your browser and needs JavaScript.

What you’ll learn

• Static friction matches the push, up to $\mu_\text{s} N$. Kinetic friction while sliding is $\mu_\text{k} N$.
• Usually $\mu_\text{k} < \mu_\text{s}$: starting something moving is harder than keeping it moving.
• Friction always opposes sliding or attempted sliding.

Steps

1. Get it moving
2. Static friction holds on
3. A gentle push
4. Sliding friction
5. Keep pushing
6. The heavy sofa
7. Anti-lock brakes