IB Physics SL A.2.22 Collision energy

Practise collision-energy questions by comparing kinetic energy before and after impact, then linking any loss to physical changes.

Exam points

calculate total KE before and after using 1/2mv^2, then find the energy loss in joules
use momentum first to get a shared speed, then calculate the KE ratio or percentage loss
state an energy pathway such as deformation or heating, linked to the impact model assumption

[Maximum number: 3]

A horizontal rigid bar of length 2 R is pivoted at its centre. The bar is free to rotate in a horizontal plane about a vertical axis through the pivot. A point particle of mass M is attached to one end of the bar and a container is attached to the other end of the bar.

A point particle of mass $\frac{M}{3}$ moving with speed v at right angles to the rod collides with the container and gets stuck in the container. The system then starts to rotate about the vertical axis.

The mass of the rod and the container can be neglected.

Figure for Question A.2.22—Collision energy question 1 — IB Physics SL

Determine in terms of M and v the energy lost during the collision.

$\begin{aligned} \text { initial } K E=\frac{M v^{2}}{6} \text { final } K E=\frac{M v^{2}}{24} \end{aligned}$

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A.2.22—Collision energy question 1