Give an example of a situation in which there is a force and a displacement, but the force does no work. Explain why it does no work.

Solution 2CQ

Work is said to be done by a force on an object when the force acts on the object and displaces it from its position. When a force acts on an object and displaces it by a distance , then the work done is expressed as , where is the angle between the force and the displacement.

Step 1 of 2

Suppose you lift a bag of books and start walking on a horizontal floor. Now analyze the directions of the force and the displacement. Let us have a look at the following figure to understand the situation.

From the figure above, you have applied a force on the bag in the upward direction. You are walking along the floor as shown above. So, the force and displacement are mutually perpendicular. So, the angle between them is .

According to , when

Hence the work done by you on the bag is zero.