2 Particles \(P\) and \(Q\), of masses 0.45 kg and \(m \mathrm {~kg}\) respectively, are attached to the ends of a light inextensible string which passes over a small smooth pulley. The particles are released from rest with the string taut and both particles 0.36 m above a horizontal surface. \(Q\) descends with acceleration \(0.98 \mathrm {~m} \mathrm {~s} ^ { - 2 }\). When \(Q\) strikes the surface, it remains at rest.

1. Calculate the tension in the string while both particles are in motion.
2. Find the value of \(m\).
3. Calculate the speed at which \(Q\) strikes the surface.
4. Calculate the greatest height of \(P\) above the surface. (You may assume that \(P\) does not reach the pulley.)