MEPX
Chapter 7 of 10All chapters
  1. 1Describing motion
  2. 2The laws of motion
  3. 3Free body diagrams
  4. 4Friction and normal forces
  5. 5Equilibrium and torque
  6. 6Work and energy
  7. 7Momentum and collisions
  8. 8Circular motion
  9. 9Projectiles
  10. 10Solving problems

Chapter 7 of 10

Momentum and collisions

What survives an impact.

Conservation

Total momentum before a collision equals total momentum after, whatever happens during it. That holds even when energy is lost as heat and noise.

  • Elastic collisions conserve kinetic energy too; most real ones do not.
  • Impulse is force times time and equals the change in momentum.

Why it matters

Crumple zones, airbags and landing by bending your knees all work by extending the time of the change, which reduces the force for the same change in momentum.