7 A particle moves in a straight line starting from rest from a point \(O\). The acceleration of the particle at time \(t \mathrm {~s}\) after leaving \(O\) is \(a \mathrm {~m} \mathrm {~s} ^ { - 2 }\), where
$$a = 5.4 - 1.62 t$$
- Find the positive value of \(t\) at which the velocity of the particle is zero, giving your answer as an exact fraction.
- Find the velocity of the particle at \(t = 10\) and sketch the velocity-time graph for the first ten seconds of the motion.
- Find the total distance travelled during the first ten seconds of the motion.
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