College Physics 10th Edition by Raymond Serway,Chris Vuille

Exercise 74

A small block of mass m and charge Q is placed on an insulated, frictionless, inclined plane of angle as in Figure P15.21. An electric field is applied parallel to the incline. (a) Find an expression for the magnitude of the electric field that enables the block to remain at rest. (b) If m = 5.40 g, Q = 7.00 C, and = 25.0°, determine the magnitude and direction of the electric field that enables the block to remain at rest on the incline.