1. The problem statement, all variables and given/known data In the arrangement as shown in the figure below, the ends P and Q of an inextensible string move downwards with uniform speed u. Pulleys A and B are fixed. Mass M moves upward with a speed: a. 2ucosθ b. u/cosθ c. 2u/cosθ d. ucosθ 2. Relevant equations None, I am not sure whether it falls under general physics or homework section. 3. The attempt at a solution The strings move with velocity u in their respective directions , thus block will move with velocity 2ucosθ. Since each of the two strings has velocity in vertical direction as ucosθ . But the answer says it is u/cosθ . Which seems right as when you take components of this total velocity of block M in directions of strings, it gives components as u, but those 2 components don't add up to 2ucosθ. What is the mistake here ? Why are they not adding up to ucosθ? Thank you for all the support and help.