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    Hi, I worked out a question in the revision guide of edexcel AS mechanics and I got the answer 50 but in the answers it says that it is 42 not 50. I have no idea how that answer could be worked out. Please help me. This is the question:

    A car is travelling along a straight motorway at a constant speed V m/s. Ten seconds after passing a speed-limit sign, the driver brakes and the car decelerates uniformly for 5 seconds, reducing its speed to 30m/s. Given that the car covers a distance of 600m in the 15 second period, find the value of V.

    Anyone, suggestions please?
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    Show me your working out

    It helps to sketch a velocity-time graph where the area under the graph is the displacement covered.
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    (Original post by ManLike007)
    Show me your working out

    It helps to sketch a velocity-time graph where the area under the graph is the displacement covered.
    I drew a velocity-time graph and calculated the area.
    600=1/2 * (V-30) * 15 + 30*15
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    (Original post by Rashina)
    I drew a velocity-time graph and calculated the area.
    600=1/2 * (V-30) * 15 + 30*15
    Your calculation of the area of a trapezium looks wrong


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    (Original post by gdunne42)
    Your calculation of the area of a trapezium looks wrong


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    Thank you.Now I got it correct. I got the answer.
 
 
 
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