IB Physics SL A 2 20 Elastic and Inelastic Collisions Questions

Practise distinguishing elastic and inelastic collisions using momentum, kinetic energy and rebound evidence.

Exam points

Distinguish elastic and inelastic collisions of two bodies using momentum and kinetic-energy outcomes.
Calculate and interpret momentum, kinetic-energy retention or dissipation in collision evidence, stating conservation assumptions.

[Maximum number: 3]

A second identical ball is placed at the bottom of the bowl and the first ball is displaced so that its height from the horizontal is equal to 8.0 m .

Figure for Question IB Physics SL A 2 20 Elastic and Inelastic Collisions Questions question 1 — IB Physics SL

The first ball is released and eventually strikes the second ball. The two balls remain in contact. Determine, in m , the maximum height reached by the two balls.

$\text { speed before collision } v=\ll \sqrt{2 g R}=>12.5<\mathrm{ms}^{-1} \gg$

«from conservation of momentum» common speed after collision is $\frac{1}{2}$ initial
$\begin{aligned} & \text { speed }<v_{c}=\frac{12.5}{2}=6.25 \mathrm{~ms}^{-1} \gg & h=<\frac{v_{c}^{2}}{2 g}=\frac{6.25^{2}}{2 \times 9.81}>2.0<\mathrm{m} \gg \end{aligned}$

Allow 12.5 from incorrect use of kinematics equations

Award [3] for a bald correct answer Award [0] for m g(8)=2 m g h leading to h=4 m if done in one step.

Allow ECF from MP1

Allow ECF from MP2

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IB Physics SL A 2 20 Elastic and Inelastic Collisions Questions question 1