Two particles \(P\) and \(Q\), of mass \(m\) and \(k m\) respectively, are travelling in opposite directions on a straight horizontal path with speeds \(3 u\) and \(2 u\) respectively. \(P\) and \(Q\) collide and, as a result, the direction of motion of both particles is reversed and their speeds are halved.
- Find the value of \(k\).
- Write down an expression in terms of \(m\) and \(u\) for the magnitude of the impulse which \(P\) exerts on \(Q\) during the collision.
(3 marks)
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\caption{Fig. 1}
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Figure 1 shows a plank \(A B\) of mass 40 kg and length 6 m , which rests on supports at each of its ends. The plank is wedge-shaped, being thicker at end \(A\) than at end \(B\).
A woman of mass 60 kg stands on the plank at a distance of 2 m from \(B\).