Physics Q1 – NEET-UG 2023

Home Physics Mechanical Properties of SolidsQuestion #290

Let a wire be suspended from the ceiling (rigid support) and stretched by a weight

W

attached at its free end. The longitudinal stress at any point of cross-sectional area

A

of the wire is :

Clue 1 of 3: Definition of Stress

Stress is a measure of the internal forces that particles of a continuous material exert on each other, resisting deformation.

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Ninja Strategy•Fundamental Definition

Recall the basic definition of longitudinal stress as force per unit area and directly apply the given weight as the force.

🧠 Full Solution Path

Step 1: Define Longitudinal Stress✦ Active

Longitudinal stress ( $σ$ ) is the internal restoring force per unit cross-sectional area ( $A$ ) developed in a body when subjected to an external deforming force ( $F$ ). The formula for stress is:

σ = \frac{F}{A}

Step 2: Identify Force and Area○ Expand

The problem states that a wire is stretched by a weight $W$ attached at its free end. Therefore, the deforming force $F$ acting on the wire is equal to the weight $W$ . The cross-sectional area of the wire is given as $A$ .

💡 Teacher's Secret Hint

Remember that weight is a force due to gravity.

Step 3: Calculate Stress○ Expand

Substitute the identified force ( $F = W$ ) and area ( $A$ ) into the stress formula:

σ = \frac{W}{A}

This matches option (2).

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Physics Question 1 – NEET-UG 2023

Clue 1 of 3: Definition of Stress

🧠 Full Solution Path