7.
\includegraphics[max width=\textwidth, alt={}, center]{31efa627-5114-4797-9d46-7f1311c18ff8-2_456_380_1862_395} A particle \(P\), of mass 4 kg , rests on horizontal ground and is attached by a light, inextensible string to another particle \(Q\) of mass 4.5 kg . The string passes over a smooth pulley whose centre is 3 m above the ground. Initially \(Q\) is 1.1 m below the level of the centre of the pulley. The system is released from rest in this position.

1. Find the acceleration of the two particles.
2. Find the speed with which \(Q\) hits the ground. Assuming that \(Q\) does not rebound from the ground while the string is slack,
3. show that \(P\) does not reach the pulley before \(Q\) starts to move again.
4. Find the speed with which \(Q\) leaves the ground when the string again becomes taut.
   (3 marks)