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A wire of length L and radius r is clamped at one end. If its other end is pulled by a force F, its length increases by l. If the radius of the wire and the applied force both are reduced to half of their original values keeping original length constant, the increase in length will become:

Solution & Explanation

### Related Formula Young's modulus Y is defined as: Y = fractextStresstextStrain = fracF / Al / L = fracF LA l Solving for the extension l: l = fracF LA Y = fracF Lpi r^2 Y Since the material does not change, Y remains constant. ### Core Logic Let the original parameters be F, r, L, l. The extension is: l = fracF Lpi r^2 Y quad dots (i) When the force and radius are both halved, keeping original length L and Young's Modulus Y constant: * New Force, F' = fracF2 * New Radius, r' = fracr2 The new extension l' is: l' = fracF' Lpi (r')^2 Y = frac(F/2) Lpi (r/2)^2 Y l' = fracF L / 2pi r^2 Y / 4 = 2 left( fracF Lpi r^2 Y right) ### Step 1: Calculate Final Extension Comparing this with equation (i): l' = 2l Thus, the increase in length becomes 2text times its original value. ### Pattern Recognition From the formula l propto fracFr^2, if F is scaled by frac12 and r by frac12, the scaling factor for l is frac1/2(1/2)^2 = 2 directly. ### Evaluation Rubric / Model Answer null ### Chapter Mix Class 11 Physics: Mechanical Properties of Solids

Reference Study Guides

More Mechanical Properties of Solids Previous-Year Questions — Page 2

Q24 jee_main_2025_24_jan_evening Bulk Modulus
The increase in pressure required to decrease the volume of a water sample by 0.2% is P times 10^5 Nm ^-2 . Bulk modulus of water is 2.15 times 10^9 Nm ^-2 . The value of P is ____.
Numerical Answer. Answer: 43 to 43

Solution

### Related Formula Bulk Modulus formula: B = - fracDelta PfracDelta VV implies Delta P = B left( frac-Delta VV ight) ### Core Logic Given specifications: - Fractional volume drop, frac-Delta VV = 0.2\% = frac0.2100 = 2 times 10^-3 - Bulk modulus value, B = 2.15 times 10^9\ mathrmN/m^2 Calculating excess pressure: Delta P = 2.15 times 10^9 times 2 times 10^-3 Delta P = 4.3 times 10^6\ mathrmN/m^2 = 43 times 10^5\ mathrmN/m^2 Comparing with P times 10^5, we get P = 43. ### Pattern Recognition Bulk modulus measures a fluid's resistance to compression. A tiny percentage reduction in volume requires a massive amount of pressure due to water's near-incompressibility. ### Evaluation Rubric / Model Answer null ### Chapter Mix Class 11 Physics: Mechanical Properties of Solids
Q23 jee_main_2025_28_jan_evening Bulk Modulus
The volume contraction of a solid copper cube of edge length 10mathrmcm , when subjected to a hydraulic pressure of 7 times 10^6mathrmPa , would be ____________ mm^3 . (Given bulk modulus of copper = 1.4 times 10^11 mathrmNm^-2 )
Numerical Answer. Answer: 50

Solution

### Related Formula Bulk modulus B measures a material's resistance to uniform compression and is defined as the ratio of hydraulic pressure to volumetric strain: B = fracDelta Pleft(fracDelta VVright) implies Delta V = fracDelta P cdot VB ### Core Logic Given parameters [cite: 192, 193]: * Edge length of the cube, a = 10 text cm = 0.1 text m * Initial volume, V = a^3 = (0.1)^3 = 10^-3 text m^3 = 10^6 text mm^3 * Hydraulic pressure increase, Delta P = 7 times 10^6 text Pa * Bulk Modulus, B = 1.4 times 10^11 text N/m^2 Substitute these values into the volume change equation : Delta V = frac7 times 10^6 times 10^-31.4 times 10^11 Delta V = frac7 times 10^31.4 times 10^11 = 5 times 10^-7 text m^3 quad text Convert the volume contraction into textmm^3: Delta V = 5 times 10^-7 times (10^3)^3 text mm^3 = 5 times 10^-7 times 10^9 text mm^3 = 50 text mm^3 ### Pattern Recognition Always perform unit conversions carefully at the final step to avoid handling complex decimals during calculations. Converting 1 text m^3 = 10^9 text mm^3 ensures a clean, error-free conversion. ### Evaluation Rubric / Model Answer null ### Chapter Mix Class 11 Physics: Mechanical Properties of Solids
Q jee_main_2025_29_jan_morning Elasticity
The fractional compression left(fracDeltamathrmVmathrmVright) of water at the depth of 2.5mathrmkm below the sea level is \% Given, the Bulk modulus of water = 2times 10^9mathrmNm^-2 , density of water = 10^3mathrmkgmathrmm^-3 , acceleration due to gravity = mathrmg = 10mathrmms^-2 .
  • A. 1.75
  • B. 1.0
  • C. 1.5
  • D. 1.25

Solution

### Related Formula B = fracDelta Pleft(fracDelta VVright) = fracrho g hleft(fracDelta VVright) ### Core Logic Calculate the hydrostatic pressure change at depth h = 2.5text km = 2500text m : Delta P = rho g h = 10^3 cdot 10 cdot 2500 = 2.5 times 10^7 mathrm~Ncdot m^-2 Now compute the percentage fractional compression : fracDelta VV times 100 = fracDelta PB times 100 = frac2.5 times 10^72 times 10^9 times 100\% = 1.25\% ### Chapter Mix Class 11 Physics: Mechanical Properties of Solids Class 11 Physics: Mechanical Properties of Fluids
Q31 jee_main_2024_01_february_morning Elastic Moduli
With rise in temperature, the Young's modulus of elasticity:
  • A. changes erratically
  • B. decreases
  • C. increases
  • D. remains unchanged

Solution

### Related Formula Intermolecular forces weaken as thermal agitation increases: Y = fractextStresstextStrain ### Core Logic When temperature rises, the mean separation between atoms or molecules increases due to thermal expansion. This weakens the intermolecular binding forces, making the material easier to deform for the same amount of applied stress. Consequently, the value of Young's modulus decreases with a rise in temperature. ### Step 1: Final Conclusion Thus, Young's modulus of elasticity decreases with the increase in temperature. ### Pattern Recognition Temperature up rightarrow Thermal expansion up rightarrow Intermolecular bonds weaken rightarrow Modulus of elasticity down. ### Evaluation Rubric / Model Answer null ### Chapter Mix Class 11 Physics: Mechanical Properties of Solids

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