Under which of the following conditions is workdone

Analysis of the Question

In Physics, work is defined as the product of the force applied to an object and the displacement (distance moved) in the direction of that force. The formula is:

Where:

• W = Work done
• F = Force applied
• d = Displacement
• θ = Angle between force and displacement

For work to be done, there must be displacement. If you apply a force but the object does not move ($d = 0$), then the work done is zero.

Explanation of Concepts

• Option A: The man is applying an upward force to support the load, but the load is stationary (no displacement). Therefore, $W = 0$.
• Option B: When a boy climbs onto a table, he exerts a force to lift his body weight against gravity, and his body moves through a vertical distance (displacement). Since both force and displacement are present, work is done.
• Option C: Pushing against a heavy table that does not move means the displacement is zero. Therefore, $W = 0$.
• Option D: Holding a pot of water requires force, but because the pot is held stationary, there is no displacement. Therefore, $W = 0$.

Step-by-Step Solution

1. Identify the requirement: Work is only done when an object moves in the direction of the force applied.
2. Evaluate each scenario: • A: No movement = No work. • B: Movement occurs as the boy climbs = Work is done. • C: No movement = No work. • D: No movement = No work.
3. Conclusion: Only in option B does the application of force result in a change in position (displacement).

Exam Tip

Always remember the "Physics definition" of work: Work = Force × Distance. If you are tired from holding a heavy bag but you haven't moved an inch, a physicist would say you have done "zero work," even if your muscles feel exhausted! Look for the option where movement (displacement) actually occurs.