Fig. 7.1 shows a child sitting on a sledge on a snow-covered hill of constant slope. At time t = 0, the child and the sledge begin to move down the hill in a straight line. When the child sees a wall ahead, he applies the brake. The child and sledge continue to travel in a straight line until they come to a stop before hitting the wall.

1. (a)Fig 7.2 shows how the speed of the child and sledge varies over the whole of the journey. Explain why, between t = 0 and t = 26 s, the speed varies in the way shown by the graph.[3]
2. (b)At t = 26s, the front of the sledge is 35m from the wall. Determine the distance between the front of the sledge and the wall when the sledge stops.[3]
3. (c)(i)Determine the size of the deceleration.[3]
4. (c)(ii)The mass of the child is 46 kg and the mass of the sledge is 9.0 kg. Calculate the resultant force on the child and sledge as they decelerate.[2]
5. (c)(iii)State the energy transfer that is taking place as the child and sledge decelerate.[2]
6. (d)At t = 26 s, when the brake is first applied, the child jerks forwards on the sledge. Explain why.[2]

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