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Saturday, 31 October

JEE Main 2021 · PhysicsMultiple choiceSingle correctEasyCalculation

JEE Main 26 February 2021, Shift 2, Physics Q15

Question 15 of 90 in this shift, Physics question 15 of 30, Section A.

The length of metallic wire is l1l_1 when tension in it is T1T_1. It is l2l_2 when the tension is T2T_2. The original length of the wire will be :
  1. (1)l1+l22\frac{l_1 + l_2}{2}
  2. (2)T2l1+T1l2T1+T2\frac{T_2 l_1 + T_1 l_2}{T_1 + T_2}
  3. (3)T1l1−T2l2T2−T1\frac{T_1 l_1 - T_2 l_2}{T_2 - T_1}
  4. (4)T2l1−T1l2T2−T1\frac{T_2 l_1 - T_1 l_2}{T_2 - T_1}Official answer

Official answer

Option 4

NTA final key.

Chapter
Mechanical Properties of Solids
Topic
Elasticity
Idea tested
Finding Natural Length from Two Tensions

Same idea in other shifts

Asked 3× in all
  1. 2 Apr 2025, Shift 2 · Q48The 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.…EasyNumerical value
  2. 29 Jun 2022, Shift 1 · Q36A wire of length L is hanging from a fixed support. The length changes to L1L_1 and L2L_2 when masses 1 kg and 2 kg are suspended…MediumSingle correct

Question text from the official JEE Main paper published by NTA; answer from the final answer key. Chapter, topic and idea tags, difficulty and skill are Lumi’s. Lumi analyses 108 of the 174 JEE Main shifts held from 2017 to 2026.