So the below is a question from the June 2007 Edexcel paper that I have a problem with.The only part I cannot do is the last part but I included the whole question so people can see it in context.
My problem is - how do you know when the string is taut again? I assumed the string would be taut again when Q stopped moving but according to the markscheme that is wrong :3
Two particles P and Q have mass 0.5 kg and m kg respectively, where m < 0.5. The particles are connected by a light inextensible string which passes over a smooth, fixed pulley. Initially P is 3.15 m above horizontal ground. The particles are released from rest with the string taut and the hanging parts of the string vertical, as shown in Figure 4. After P has been descending for 1.5 s, it strikes the ground. Particle P reaches the ground before Q has reached the pulley.
(a) Show that the acceleration of P as it descends is 2.8 m s–2.
(3)
(b) Find the tension in the string as P descends.
(3)
(c) Show that m = 5/18.
(4)
(d) State how you have used the information that the string is inextensible.
(1)
When P strikes the ground, P does not rebound and the string becomes slack. Particle Q then moves freely under gravity, without reaching the pulley, until the string becomes taut again.
(e) Find the time between the instant when P strikes the ground and the instant when the string becomes taut again.
(6)