Question

A force acting on an object does no work if1. a machine is used to move the object.2. the force is greater than the force of friction.3. the force acts perpendicular to the direction of the object’s motion.4. the object accelerates.

Answer 1

The work done of any object is defined by

$W=Fd\cos \theta$

Here, F is the force acting on the object.

d is the displacement of the object due to the force applied.

$\theta$

is the angle between force and displacement.

For work done to become zero, the applied force can be zero, or displacement can be zero, or cosine angle is zero.

Cosine angle can be zero if force and displacement are perpendicular to each other.

Thus, if the force acts perpendicular to the direction of the object's motion, no work is done..