Collisions Topic Review summary

Key learning points

• Conservation of momentum along the line of centres (no external impulse).
• Newton’s law of restitution: $e=\\frac{\\text{speed of separation}}{\\text{speed of approach}}$.
• $0\\le e\\le 1$; $e=0$ inelastic sticking (in 1D if they coalesce), $e=1$ kinetic energy conserved.
• Take approach/separation as positive magnitudes carefully with signs.
• Successive collisions: update velocities between impacts.

Worked example 1 — e

Approach 6 m/s, separation 3 m/s. $e$?

Working

Ratio of relative speeds.

Worked example 2 — KE

When is KE conserved in a collision?

Working

Otherwise loss of KE to heat/deformation.

Worked example 3 — Conservation of momentum along the line of

Apply this idea from the Topic Review: Conservation of momentum along the line of centres (no external impulse).

Working

Attempt without notes, then check the answers PDF.

Worked example 4 — Newton’s law of restitution: e=\\\\\\\text

Newton’s law of restitution: $e=\\\\frac{\\\\text{speed of separation}}{\\\\text{speed of approach}}$.

Working

Attempt without notes, then check the answers PDF.

Scaffolded Learning Sheet and answers (PDFs)

This page is a short, searchable overview for revision and search engines. Use the Scaffolded Learning Sheet first, then the Answers PDF for a full written solution. The printable PDFs remain the main classroom resource.