Question

Why is it important that the works is done in the direction of motion? What happens to the work done in the perpendicular direction?

Answer 1

If displacement and velocity of the particle are in the same direction due to the force then there is work done by the force but if the displacement and velocity are in perpendicular then there is no work done by the force. This is due to x,y,z components of force,velocity,displacement are completely ndependent of each other. Suppose a force is in the x direction then there will not be any displacement in y and z directions.So there will not be any work done in perpendicular directions.