Two charged pith balls are suspended on very light 120cm strings. Each has a mass of 10.0g. Assume the angle the threads make from the vertical is theta= 15 degrees and that the balls are in equilibrium. Draw a free body diagram for one of the pith balls and clearly label all forces with magnitude and direction. Assuming the pith balls are equally charged, what is the charge on each ball? (This is not a qualitative prediction; a numerical answer must be obtained.) Please show all work. I am lost on how to do the problem

## Answer

Draw the following free body diagram for the right ball from given data. 0 T sin θ Here, / is the length of the string, 2r is the separation between the ball, m is the mass of the ball, 7is the tension and FE 1s the electrostatic force The sing angle from the above figure is. – (1.2m)sin 15 0.31m Since the ball is in equilibrium, the net force on the ball in vertical and horizontal direction must be zero The net force on the ball in horizontal direction is equal to zerd FE-Tsin 9-0 T sin 6- F

The net force on the ball in vertical direction is equal to zero. ly T cos e mg Take the ratio of above two equations FE=mg tan θ mg tan θ (27). 10×10-3kg (9.8 m/s2 )tan 15 98109 N·m 2 /C2 -2(0.31m -1.06×10-6C