https://www.physicsforums.com/attachment.php?attachmentid=4204&stc=1 Both mass of A and B is 0.49kg. A ring of 0.001kg is added on A to let A begin to move downward. (a) what is the time needed for A to move 50cm downward? (b)What is the time needed for A to move another 50cm downward if the ring was taken off imediately after first 50cm? I can find the the answer of (a) but i dont know how to solve the 2nd question since I have no idea at all about how to find out the acceleration after first 50cm. Can anyone help me?