Classify an interaction
Compare elastic, partially inelastic, and sticking collisions using recorded evidence.
AP Physics 1 · Unit 4 · Linear Momentum
Elastic Collisions
Compare collisions, track momentum and kinetic energy, and predict how mass and initial velocity affect the rebound.
Start lesson- Free
- No account required
- Self-paced
Start guided lesson
Learn by doing
Three ideas you’ll put into motion
Predict final velocities
Combine momentum and kinetic-energy conservation for an ideal elastic collision.
Follow stored energy
Investigate spring compression and the motion that remains when the spring is most compressed.
The big idea
The key ideas, at a glance.
Elastic collisions preserve kinetic energy
With negligible external impulse, system momentum is conserved. An ideal elastic collision also conserves the system’s total kinetic energy.
Equal masses provide a useful case
In an ideal one-dimensional elastic collision between equal masses, the objects exchange velocities. Other mass ratios produce different results.
A quick comparison
One of two equal-mass carts is initially at rest before an ideal elastic collision.
The moving cart can stop while the other takes its velocity.
Teaching this topic?Classroom fit, AP connections, and support
- Classroom fit
- Use for a concept introduction, guided independent practice, or a projected class discussion.
- Before students begin
- Momentum conservation, kinetic and elastic potential energy, and center-of-mass velocity.
- Built-in support
- Prepared scenes, guided prompts, and feedback on lesson questions.
- AP Physics 1 connections
- Unit 4: elastic and inelastic collisions, with energy connections.
- Check for understanding
- Ask which conservation rule still applies in a sticking collision with negligible external impulse.
- Optional extension
- Try more mass combinations in the One-Dimensional Collision lab.
Ready to test your thinking?
The first scene is set up. Start the lesson and explore.