Two wires A and B are made of same material having ratio of lengths fracmathrmL_mathrmAmathrmL_mathrmB = frac13 and their diameters ratio fracmathrmd_mathrmAmathrmd_mathrmB = 2 . If both the wires are stretched using same force, what would be the ratio of their respective elongations?

Solution & Explanation

### Related Formula Young's modulus Y is defined as: Y = fractextStresstextStrain = fracF / ADelta L / L implies Delta L = fracF LA Y Area of cross-section of wire with diameter d is: A = fracpi d^24 implies Delta L = frac4 F Lpi d^2 Y ### Core Logic Since both wires are made of the same material (Y_A = Y_B) and stretched with the same force (F_A = F_B): Delta L propto fracLd^2 Set up the ratio for wires A and B: fracDelta L_ADelta L_B = left( fracL_AL_B right) times left( fracd_Bd_A right)^2 ### Step 1: Substitute Given Ratios Substitute the ratios \frac{L_A}{L_B} = \frac{1}{3} and \frac{d_A}{d_B} = 2 \implies \frac{d_B}{d_A} = \frac{1}{2}: fracDelta L_ADelta L_B = left( frac13 right) times left( frac12 right)^2 = frac13 times frac14 = frac112 Therefore, the ratio of their elongations is 1:12. ### Pattern Recognition Sees: Same material, same stretching force. Shortcut: Elongation scales directly with length and inversely with the square of the diameter (radius). Thus, ratio is (1/3) / (2^2) = 1/12$. ### Evaluation Rubric / Model Answer null ### Chapter Mix Class 11 Physics: Mechanical Properties of Solids

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More Mechanical Properties of Solids Previous-Year Questions — Page 4

Q58 jee_main_2024_31_jan_morning Bulk Modulus
The depth below the surface of sea to which a rubber ball be taken so as to decrease its volume by 0.02\% is ________ mathrmm. (Take density of sea water = 10^3mathrm\ kgm^-3, Bulk modulus of rubber = 9 times 10^8mathrm\ Nm^-2, and g = 10mathrm\ ms^-2)
Numerical Answer. Answer: 18 to 18

Solution

### Related Formula beta = frac-Delta PfracDelta VV Delta P = rho g h ### Core Logic The change in pressure Delta P is the hydrostatic pressure at depth h. Delta P = -beta fracDelta VV rho g h = -beta fracDelta VV ### Step 2: Calculation Given values: rho = 10^3mathrm\,kg/m^3 g = 10mathrm\,m/s^2 beta = 9 times 10^8mathrm\,N/m^2 fracDelta VV = -0.02\% = -frac0.02100 Substitute into the equation: 10^3 times 10 times h = - (9 times 10^8) times left(-frac0.02100right) 10^4 times h = 9 times 10^8 times 2 times 10^-4 10^4 h = 18 times 10^4 h = 18mathrm\,m ### Evaluation Rubric / Model Answer null ### Chapter Mix Class 11 Physics: Mechanical Properties Of Solids Class 11 Physics: Mechanical Properties Of Fluids

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