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Saturday, 31 October

JEE Main 2021 · PhysicsNumerical answerNumerical valueMediumMulti-step

JEE Main 27 August 2021, Shift 2, Physics Q24

Question 24 of 90 in this shift, Physics question 24 of 30, Section B.

Wires W1W_1 and W2W_2 are made of same material having the breaking stress of 1.25×109 N/m21.25\times10^9\ \mathrm{N/m^2}. W1W_1 and W2W_2 have cross-sectional area of 8×10−7 m28\times10^{-7}\ \mathrm{m^2} and 4×10−7 m24\times10^{-7}\ \mathrm{m^2}, respectively. Masses of 20 kg and 10 kg hang from them as shown in the figure. The maximum mass that can be placed in the pan without breaking the wires is __________ kg. (Use g=10 m/s2g=10\ \mathrm{m/s^2})

The figure, in words

A vertical chain from a fixed support: wire W1 hangs from the ceiling and holds a 20 kg block; wire W2 hangs from the 20 kg block and holds a 10 kg block; below the 10 kg block a string holds a pan.

Official answer

40

NTA final key.

Chapter
Mechanical Properties of Solids
Topic
Elasticity
Idea tested
Breaking Stress and Breaking Force

Same idea in other shifts

Asked 7× in all
  1. 5 Apr 2026, Shift 1 · Q43Two wires as shown in the figure below, made of steel and have breaking stress of 12×108 N/m212 \times 10^8\ \mathrm{N/m^2}. Area of cross-section…MediumSingle correctHas a figure
  2. 6 Apr 2026, Shift 1 · Q30A lift of mass 1600 kg is supported by thick iron wire. If the maximum stress which the wire can withstand is 4×1084\times10^8 N/m2^2 and…MediumSingle correct
  3. 26 Jul 2022, Shift 2 · Q50The area of cross section of the rope used to lift a load by a crane is 2.5×10−4m22.5 \times 10^{-4}m^2. The maximum lifting capacity of the crane…EasySingle correct
  4. 29 Jul 2022, Shift 2 · Q53A metal wire of length 0.5 m and cross-sectional area 10−4 m210^{-4}\ \mathrm{m^2} has breaking stress 5×108 Nm−25\times10^8\ \mathrm{Nm^{-2}}. A block…MediumNumerical value
  5. 26 Aug 2021, Shift 2 · Q13Two blocks of masses 3 kg and 5 kg are connected by a metal wire going over a smooth pulley. The breaking stress of the metal is…MediumDiagram basedHas a figure
  6. 9 Jan 2020, Shift 1 · Q23A body of mass m=10 kg is attached to one end of a wire of length 0.3 m. The maximum angular speed (in rad s−1\mathrm{s^{-1}}) with which…MediumNumerical value

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. This question needs a figure we do not reproduce; it is described in words above. Lumi analyses 108 of the 174 JEE Main shifts held from 2017 to 2026.