The problem is: A small block with mass 0.280kg is attached to a string passing through a hole in a frictionless, horizontal surface. The block is originally revolving in a circle with a radius of 0.820m about the hole with a tangential speed of 4.50m/s. The string is then pulled slowly from below, shortening the radius of the circle in which the block revolves. The breaking strength of the string is 25.0N. Well I am really unsure how to proceed with this question. The way I attempted it was trying to find the tension in the string. For that I used the normal acceleration (v^2/r) times the mass. From there I found at the breaking point the acceleration would have to be like 89.29 m/s^2 for the tension to equal 25.0N. Assuming this was all correct I still don't know how to find how the speed changes with the shortening of the radius.