Hi guys, I'm stuck at this 2 questions for a while. 1. A mass suspended from a vertical spring is displaced vertically downwards by a distance A and released. It executes simple harmonic motion about its equilibrium position O. Given that time taken for the mass to move through a distance of 0.5A from the point of release is t, what is the period of the oscillation of the mass? I drew the cosine curve and at 0.5A, the corresponding time is a unknown, but it is >T/8 where T is the period. How do I carry on from here? 2. Over a period of 6 seconds, a current is uniformly reduced from 150mA to 30mA. WHat is the charge that flows during this time? The worked solutions is (150-30)6 = 720mC. 720-150-30 = 540mC which is the answer. Why is this so? I would have thought that 720 is the reduction in charge? And why the subtraction of 150 and 30? Thanks for the help in advance.