Glancing Collisions

Momentum as a vector

An interactive lesson with 6 steps, about 5 minutes: you predict, drag and solve, with instant feedback on every answer. It runs in your browser and needs JavaScript.

What you’ll learn

• In 2D, momentum is conserved in each direction separately.
• The struck ball moves along the line of centres.
• Equal masses, elastic, one at rest: they separate at 90°.

Steps

1. Momentum has direction
2. Cut it into the pocket
3. Check the momentum
4. Why 90°?
5. A thin cut
6. A head-on hit