1. The problem statement, all variables and given/known data A box of mass M is at rest on a horizontal table. The coefficient of static friction between the box and the table is k. The box is connected by a taut string to a block of unknown mass m , initially held horizontally as shown and then released. The box begins to slide at the instant the block reaches the bottom point of its swing. Find the mass m of the block. 2. Relevant equations 3. The attempt at a solution I took the force of gravity, mg, and set it equal to the friction force between the box and the table, kMg, getting m=k*M.