Aball whirls around in a vertical circle at the end of a string. the other end of the string is fixed at the center of the circle. assume that the total energy of the ball-earth system remains constant. (a) what is the tension in the string at the bottom? (use the following as necessary: m for mass of the ball, g for gravitational acceleration, vb for velocity at the bottom, and r for radius of the circle.) tb = incorrect: your answer is incorrect. (b) what is the tension in the string at the top? (use the following as necessary: m, g, vt for velocity at the top, and r.) tt = (c) how much greater is the tension at the bottom? (use the following as necessary: m, g.)