Physics · Thermal Properties of Matter

JEE Main 2025 — 2 April, Evening Shift — Question 65

The length of a light string is 1.4 m when the tension on it is 5 N . If the tension increases to 7 N , the length of the string is 1.56 m . The original length of the string is $\qquad$ m.

Answer: 1

Numerical answer — enter this value.

Step-by-step solution

$I={{I}_{0}}+\text{ }\!\!\Delta\!\!\text{ }I={{I}_{0}}+\frac{T{{I}_{0}}}{AY}$ $I={{I}_{0}}\left( 1+KT \right)$

$\begin{matrix}1.4={{I}_{0}}\left( 1+5K \right)\#\left( i \right) \\\end{matrix}$

$\begin{matrix}1.56={{I}_{0}}\left( 1+7K \right)\#\left( ii \right) \\\end{matrix}$

On solving ${{I}_{0}}=1$

Answer key and solution verified before publishing.

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Exam: JEE Main 2025
Paper: 2 April, Evening Shift
Subject: Physics
Chapter: Thermal Properties of Matter
Topic: Thermal Expansion of Solids and its Applications