a small block of mass m and charge Q is placed on an insulat

a small block of mass m and charge Q is placed on an insulated, frictionless, inclined plane of angle theta. An electric field is applied parallel to the incline. (a) find an expression for the manitude of the electric field that enables the block to remain at rest. (b) if m=5.4 g, Q=-7uC, and theta=25 degrees, determine the magnitude and the direction of the electric field that enables the block to remain at rest on the incline.

Solution

The sliding force = m g * sin theta

= 5.4 * 10^-3 * 9.8 * sin 25

= 0.022 N = 22.39 * 10^-3 N

The component of force in line with the incline = 22.39 * 10^-3 [ opposite direction ]