1. The problem statement, all variables and given/known data Imagine that you swing about your head a .250 kg ball attached to the end of a string. The ball moves at a constant speed in a horizontal circle with a radius of 1.50 m. If it takes 1.20 seconds for the ball the make one revolution, (a)what is the ball's tangential speed? (b)What centripetal force are you imparting to the ball via the string? (c)Can the string be exactly horizontal. 2. Relevant equations ac=Rω Fc=mac v=Rπ 3. The attempt at a solution (a) v=rω = (1.5)(2π/1.2 sec) = 7.85 ft/sec (b) ac=Rω = 1.5 [(1 rev/1.2 seconds)(2π/ 1 rev)]^2 = 41.12 ft/sec^2 Fc=mac = (.25 kg)(41.12 ft/sec^2) = 10.28 kg (c) I have no clue at all what they want to solve... am I supposed to calculate the difference between a and b?