1. The problem statement, all variables and given/known data Two identical blocks of mass M are tied with a mass-less string of length L. If the string is pulled with a force F right at the midpoint of string L, the blocks will move towards each other. What will the velocity be when the blocks collide. The blocks start from rest and friction is not considered. 2. Relevant equations Net Force = M*a 3. The attempt at a solution The horizontal component Tx provides the horizontal acceleration to the block. and since both of them accelerate towards each other, 2Tx / M will be their horizontal acceleration towards each other. But this horizontal acceleration is not a constant, but it must keep decreasing as the horizontal component keeps on decreasing as the blocks approach and theta moves towards 90 degrees. how can we use calculus to model this situation and find out the change in velocity from the initial to final points.