A particle moves in a straight line $$\(A B\)$$. The velocity $$\(v \mathrm{~m} \mathrm{~s}^{-1}\)$$ of the particle $$\(t \mathrm{~s}\)$$ after leaving $$\(A\)$$ is given by $$\(v=k\left(t^{2}-10 t+21\right)\)$$, where $$\(k\)$$ is a constant. The displacement of the particle from $$\(A\)$$, in the direction towards $$\(B\)$$, is $$\(2.85 \mathrm{~m}\)$$ when $$\(t=3\)$$ and is $$\(2.4 \mathrm{~m}\)$$ when $$\(t=6\)$$. Find the displacement of the particle from $$\(A\)$$ when its velocity is a minimum. ........................................................................................................................................................ ........................................................................................................................................................ ........................................................................................................................................................ ........................................................................................................................................................ ........................................................................................................................................................ ........................................................................................................................................................ ........................................................................................................................................................ ........................................................................................................................................................ ........................................................................................................................................................ ........................................................................................................................................................ ........................................................................................................................................................ ........................................................................................................................................................ ........................................................................................................................................................ ........................................................................................................................................................ ........................................................................................................................................................ ........................................................................................................................................................ ........................................................................................................................................................

Mathematics
IGCSE&ALevel
CAIE
Exam No:9709_s20_qp_41 Year:2020 Question No:6(b)

Answer:

Differentiating \(v\) or completing the square for \(v\)
\(a=0.05(2 t-10)\)
Min value of \(v\) is at \(t=5\).
Displacement at \(t=5\) is \(2.58 \mathrm{~m}(2.5833 \ldots)\)

Knowledge points:

4.2.3 use differentiation and integration with respect to time to solve simple problems concerning displacement, velocity and acceleration Calculus required is restricted to techniques from the content for Paper 1: Pure Mathematics 1.

Solution:

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