Answer: the force is not in the direction of the object’s motion.
Explanation:
Work = Force. Displacement
⇒ W = F. s = F s cos θ
Thus, work is said to be done when a force displaces an object from its position in the direction of the force.
If the force is less the frictional force, the object would not move. An object accelerates when a force is applied. Sometimes, the direction of force and direction of motion is not same. In that case, no work is said to be done.
For example, when porter lifts the weight on head and moves forward. The weight is perpendicular to the direction of motion. cos 90° = 0 ⇒ W = 0
