Q. A grindstone of a radius 4 m is firstly spinning with a radius of 8 rad/s. The angular speed is then increased to 12 rad/s over next 4.0 seconds. Suppose that the angular acceleration is constant. What is the average angular speed of grindstone?
Q. A string under a tension of 76 N is used to whirl a rock in a horizontal circle of radius 3.8 m at a speed of 21.84 m/s. The string is pulled in, and the speed of the rock increases. When the string is 0.494 m long and the speed of the rock is 70.3 m/s, the string breaks. What is the breaking strength of the string?