A 500 g ball moves in a vertical circle on a 102 cm long string. The speed at the top is 4 m/s. What is the speed at the bottom? (think conservation of energy)

The experiment done in lab is repeated, using a ball that has unknown mass m. you plot your data in the form of f 2 versus m/l, with f in rev/s, m in kg, and l in m. your data falls close to a straight line that has slope 3.19 m/(kg · s2). use g = 9.80 m/s2 and calculate the mass m of the ball.