Grip

it clings, it clings — then it goes all at once.

tilt a ramp until the block finally breaks free

The angle where the block finally breaks loose is steeper than the angle it can keep sliding on once it’s already moving — two different thresholds, not one. That gap is static friction versus kinetic friction, the same reason a stuck drawer or a heavy piece of furniture takes a hard shove to start moving and then slides free all at once.

Concepts: friction.

An interactive you play with one thumb, on Wundr.