College Physics 10th Edition by Raymond Serway,Chris Vuille

تمرين 71

A small plastic ball of mass m = 2.00 g is suspended by a string of length L = 20.0 cm in a uniform electric field, as shown in Figure P15.52. If the ball is in equilibrium when the string makes a = 15.0° angle with the vertical as indicated, what is the net charge on the ball