A ball of mass `m` having a charge `q` is released from rest in a region where a horizontal electric field `E` exists.
(a) Find the resultant force acting on the ball.
(b) Find the trajectory followed by the ball.

Explanation

The forces acting on the ball are weight of the ball in vertically downward direction and the electric force in the horizontal direction.
(a) Resultant force : `F = sqrt((mg)^(2) + (qE)^(2))`.
(b) Let the ball be at point `P` after time `t`.
`x`-direction : `x = (1)/(2) (qE)/(m) t^(2)`
`y`-direction : `y = (1)/(2) g t^(2)`
`(y)/(x) = (g)/(qE//m)`
`y = (mgx)/(qE)`
Trajectory is straight line.