1 Alan, of mass 76 kg , performed a ski jump. He took off at the point \(A\) at the end of the ski run with a speed of \(28 \mathrm {~m} \mathrm {~s} ^ { - 1 }\) and landed at the point \(B\). The level of the point \(B\) is 31 metres vertically below the level of the point \(A\), as shown in the diagram. Assume that his weight is the only force that acted on Alan during the jump.
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1. Calculate the kinetic energy of Alan when he was at the point \(A\).
2. Calculate the potential energy lost by Alan during the jump as he moved from the point \(A\) to the point \(B\).
3. 1. Find the kinetic energy of Alan when he reached the point \(B\).
   2. Hence find the speed of Alan when he reached the point \(B\).