The diagram is the speed-time graph of part of a train's journey. The train slows down uniformly from a speed of 50 m/s to a speed of 10 m/s in a time of 20 seconds. During the next 30 seconds, it accelerates uniformly to a speed of u metres/second. [Figure X.X]

1. (a)Calculate the retardation from t = 0 to t = 20.[1]
2. (b)Calculate the speed of the train when t = 15.[1]
3. (c)Calculate the distance travelled by the train from t = 0 to t = 20.[1]
4. (d)The size of the acceleration is half the size of the retardation. Find the value of u.[1]

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