Edexcel A-Level Physics Elastic and Inelastic Collisions

Practise Edexcel A-Level Physics elastic and inelastic collisions by comparing total kinetic energy before and after impact.

Exam points

calculate total kinetic energy before and after a collision using half mv squared
deduce whether a collision is elastic by comparing conserved momentum and kinetic energy
explain inelastic collisions as kinetic energy transferred to other stores after impact

[Maximum number: 4]

Hockey is a sport played with a stick and a ball. The player tries to hit the ball with part of the stick called the 'heel', as shown.

Figure for Question 4.3.85 - Elastic and inelastic collisions question 1 — Edexcel A-Level Physics A2

A ball has a speed of $13 \mathrm{~ms}^{-1}$ . The heel has a momentum $p_{\text {heel }}$ of 3.0 Ns , in the direction of the dashed line, as shown.

The heel collides with the ball and stops.
The speed of the ball after being hit by the heel is $16 \mathrm{~ms}^{-1}$ .

Deduce whether the collision is elastic.
speed of heel before collision = 5.0 m s^-1

Before collision, $E_k=\tfrac12p_{\rm heel}v_{\rm heel}+\tfrac12m v_i^2=7.5+13.5=21.0\,\mathrm J$ . After collision, $E_k=\tfrac12(0.160)(16)^2=20.5\,\mathrm J$ . The values are not equal, so the collision is not elastic.

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4.3.85 - Elastic and inelastic collisions question 1