7 A particle moves in a straight line. The particle is initially at rest at a point \(O\) on the line. At time \(t \mathrm {~s}\) after leaving \(O\), the acceleration \(a \mathrm {~m} \mathrm {~s} ^ { - 2 }\) of the particle is given by \(a = 25 - t ^ { 2 }\) for \(0 \leqslant t \leqslant 9\).

1. Find the maximum velocity of the particle in this time period.
2. Find the total distance travelled until the maximum velocity is reached.
   The acceleration of the particle for \(t > 9\) is given by \(a = - 3 t ^ { - \frac { 1 } { 2 } }\).
3. Find the velocity of the particle when \(t = 25\).
   If you use the following lined page to complete the answer(s) to any question(s), the question number(s) must be clearly shown.