1. The problem statement, all variables and given/known data [PLAIN]http://img180.imageshack.us/img180/8643/mechanicsquestion.jpg [Broken] 2. Relevant equations Conservation of Energy 3. The attempt at a solution I cannot seem to understand the motion involved, especially because the string is inextensible. That means that while the string is taut, if P moves upwards, for example, Q will have to go downwards and vice versa. I tried to do it by considering conservation of energy on P only. I got the thing the question asked to show but with an extra 2gsin(theeta)sin(Beeta) at the end. So help me out please?