Question

Assertion: A weight lifter does not work in holding the weight up.
Reason: Work done is zero because distance moved is zero.
Which of the following statements is true?
A) Both assertion and reason are correct and the reason is the correct explanation for the assertion.
B) Both assertion and reason are correct and the reason is not the correct explanation for the assertion.
C) The assertion is correct but the reason is incorrect.
D) Both assertion and reason are incorrect.

Answer 1

Hint:The work done by an object depends only on the force acting on the body and the displacement it causes. So, the work done by the weight lifter will be zero if no force is exerted to hold the weight up or if there is no displacement of the weight even when a large force acts on it to hold it up.

Formula used:
-Work done by a force acting on an object is given by, $W = F \cdot d$ where $F$ is the force acting on the object and $d$ is the displacement of the body.

Complete step by step answer.
Step 1: Explain the concept of work done by the weight lifter using the formula for the work done.
Work done by the weight lifter on the weight is given by, $W = F \cdot d$ where $F$ is the force acting on the weight applied by the lifter and $d$ is the corresponding displacement.
The scenario described here involves a weightlifter holding up a weight.
A force is exerted by the weight lifter to hold up the weight. So, we have $F \ne 0$. Now, when the lifter holds up the weight, no displacement of the weight is observed. The weight remains stationary. So we have, $d = 0$.
Then we can obtain the work done by the lifter as $W = F \cdot 0 = 0$. So zero work is done by the lifter in holding the weight up.
Since the assertion mentions that zero work is done by the weight lifter, we can confirm that the assertion is true.
The reason for this assertion as we obtained is that no displacement occurs. This reason matches with the reason provided in the question. So we conclude that the assertion and the reason behind the assertion are true and correct.

Hence the correct option is A.

Additional information: The work done in a scenario is zero if
-The force acting on a body does not cause any displacement of the body.
-no friction is involved in the displacement.
-the force acting on the body acts perpendicular to the displacement of the body.

Note: Work done by the weight lifter while lifting the weight off the ground is not zero because the force exerted against the force of gravity does cause some displacement of the weight. But while holding the weight up there is no displacement. The force exerted there is used to maintain the weight in the air.