The student looked at the photograph and noticed that the angle between the paths of the two balls after the collision was not 90°. He modelled the collision on a computer.
He used the same initial conditions for ball 1 and the same value of θ. The
computer calculated the total kinetic energy after the collision for a range of
angles φ. The following graph was produced.

Measure φ from the photograph and use the graph to suggest why the angle
between the paths is not 90°.
φ = 45° to 52°
Use of graph with their angle to determine total kinetic energy after the collision
Statement that it is an inelastic collision
Or Statement that kinetic energy is not conserved
(dependent on candidate attempting MP1 and MP2)