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\includegraphics[max width=\textwidth, alt={}, center]{c7133fc4-9a14-43fd-b5ed-788da72291cd-4_512_1351_998_397} The diagram shows the velocity-time graph for the motion of a particle \(P\) which moves on a straight line \(B A C\). It starts at \(A\) and travels to \(B\) taking 5 s. It then reverses direction and travels from \(B\) to \(C\) taking 10 s . For the first 3 s of \(P\) 's motion its acceleration is constant. For the remaining 12 s the velocity of \(P\) is \(v \mathrm {~m} \mathrm {~s} ^ { - 1 }\) at time \(t \mathrm {~s}\) after leaving \(A\), where $$v = - 0.2 t ^ { 2 } + 4 t - 15 \text { for } 3 \leqslant t \leqslant 15$$

1. Find the value of \(v\) when \(t = 3\) and the magnitude of the acceleration of \(P\) for the first 3 s of its motion.
2. Find the maximum velocity of \(P\) while it is moving from \(B\) to \(C\).
3. Find the average speed of \(P\),
   (a) while moving from \(A\) to \(B\),
   (b) for the whole journey. \footnotetext{Permission to reproduce items where third-party owned material protected by copyright is included has been sought and cleared where possible. Every reasonable effort has been made by the publisher (UCLES) to trace copyright holders, but if any items requiring clearance have unwittingly been included, the publisher will be pleased to make amends at the earliest possible opportunity. Cambridge International Examinations is part of the Cambridge Assessment Group. Cambridge Assessment is the brand name of University of Cambridge Local Examinations Syndicate (UCLES), which is itself a department of the University of Cambridge. }