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I have the question "A speeding motorist is travelling at a constant speed of 40 m/s on a motorway. He passes a stationary police car, which immediately accelerates at a rate of 2.5 ms^-2 to a constant speed of 50 m/s. (Assume negligible resistive forces).

Sketch a graph to show the variation of speed against time for both vehicles. "

Is my graph correct ? With B being the police car and A the motorist.

enter image description here

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    $\begingroup$ There is no reason to neglect resistive forces when the vehicles are equipped with engines that allow them to go at constant speed anyway $\endgroup$ – Hagen von Eitzen Oct 18 '17 at 20:53
  • $\begingroup$ Yes that is true :) $\endgroup$ – Dan Oct 18 '17 at 20:56
  • $\begingroup$ I would annotate that the elbow of $B$ curve is at $t=20s$. $\endgroup$ – N74 Oct 18 '17 at 20:57
  • $\begingroup$ Why is t equal to 20s ? Thanks $\endgroup$ – Dan Oct 18 '17 at 21:40

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