Collisions summary

Key learning points

• Momentum conserved along the line of impact (no external impulse).
• $e=\frac{\text{speed of separation}}{\text{speed of approach}}$ along the line of centres.
• Take velocity signs carefully with a chosen positive direction.
• $e=1$ perfectly elastic; $e=0$ perfectly inelastic.

Worked example 1 — Restitution

Relative approach speed $6\,\mathrm{m\,s^{-1}}$, $e=\frac{1}{2}$. Separation speed?

Working

Multiply approach speed by $e$.

Worked example 2 — Momentum conserved along the line of impact (no externa

Use this method from the Collisions sheet: Momentum conserved along the line of impact (no external impulse).

Working

Each key learning point matches a question type on the printable worksheet.

Worked example 3 — along the line of centres

Use this method from the Collisions sheet: $e=\frac{\text{speed of separation}}{\text{speed of approach}}$ along the line of centres.

Working

Each key learning point matches a question type on the printable worksheet.

Worked example 4 — Take velocity signs carefully with a chosen positive

Use this method from the Collisions sheet: Take velocity signs carefully with a chosen positive direction.

Working

Each key learning point matches a question type on the printable worksheet.

Worked example 5 — perfectly elastic; perfectly inelastic

Use this method from the Collisions sheet: $e=1$ perfectly elastic; $e=0$ perfectly inelastic.

Working

Each key learning point matches a question type on the printable worksheet.

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.