Question

Assertion and Reason are given in following questions. Each question have four option. One of them is correct it. (1) If both assertion and reason and the reason is the correct explanation of the Assertion. (2) If both assertion and reason are true but reason is not the correct explanation of the assertion. (3) If the assertion is true but reason is false. (4) If the assertion and reason both are false. Assertion: A weight lifter does no work in holding the weight up. Reason: Work done is zero because distance moved is zero. (A) 1 (B) 2 (C) 3 (D) 4

Short answer

The correct answer is (A) 1, as both the Assertion and Reason are true and the Reason correctly explains the Assertion.

Step-by-step solution

Assertion

A weight lifter does no work in holding the weight up.

Reason

Work done is zero because the distance moved is zero. #Phase 2: Analyzing the given options#

Option 1

If both assertion and reason are true and reason is the correct explanation of the Assertion.

Option 2

If both assertion and reason are true but reason is not the correct explanation of the assertion.

Option 3

If the assertion is true but reason is false.

Option 4

If the assertion and reason both are false. #Solution:#

Analysis of Assertion

When a weightlifter holds the weight up, there is a force exerted by the weightlifter to counteract the force of gravity. Even though the weightlifter is applying a force, the weight is not being displaced, which means there's no movement. Since work is the product of force and displacement, and there's no displacement, the work done will be zero. So, the Assertion is true.

Analysis of Reason

The work done is indeed zero because the distance the weight is moved is zero while it is being held up. The Reason is correct. Now let's compare the given options with our analysis: - Option 1: Both Assertion and Reason are true, and Reason is the correct explanation of the Assertion. - Options 2, 3, and 4 do not match our analysis since both Assertion and Reason are true and Reason is indeed the correct explanation. Therefore, the answer to this exercise is \( \boxed{\textbf{(A) 1}} \).

Key concepts

Assertion and Reason Questions

Assertion and Reason questions are designed to test the understanding of concepts and their interrelationships. In such questions, two statements are given – an assertion and a reason. The task is to evaluate the truthfulness of both statements and determine whether the reason correctly explains the assertion.

Understanding these questions requires careful analysis of both statements. Here’s how you can master them:

• Read both the assertion and the reason carefully.
• Determine if both are true independently.
• Check if the reason provided actually explains the assertion.

In the context of physics, these questions often involve understanding fundamental principles, such as the relation between work and energy. Accurately identifying the connections between cause and effect is vital.

Work and Energy

Work and energy are core concepts in physics, fundamentally connected by how forces cause movement. Work is done when a force causes displacement. The formula for work done is given by:\[ W = F \times d \times \cos(\theta) \]where:

• \( W \) is the work done,
• \( F \) is the force applied,
• \( d \) is the displacement,
• \( \theta \) is the angle between the force and the direction of displacement.

In a scenario where a force is applied but no displacement occurs, the work done is zero. This is because without movement, no energy is transferred or transformed. Therefore, even if a weightlifter holds a weight against gravity, since the weight does not move, the work done remains zero. Understanding this helps in grasping the idea that energy needs movement to manifest work.

Force and Displacement

Force and displacement are interconnected ideas that help us understand work. Force is any interaction that changes the motion of an object. Displacement, on the other hand, refers to the change in the position of an object.

• Force alone is not enough to do work; the object must move.
• Work can only occur when displacement happens in the direction of the force.

For example, in the case of a weightlifter holding weights stationary, the force exerted counteracts gravity, but no displacement occurs. Hence, the work performed is zero. This illustrates that for work to be done, displacement in the direction of the applied force is compulsory. By understanding the relation between force and displacement, one can better appreciate how work is defined in physics.