Elasticity – JEE Main Previous Year Questions with Solutions
JEE Main Previous Year Question of Physics with Solutions are available here. Practicing JEE Main Previous Year Papers Questions of Physics will help all the JEE aspirants in realizing the question pattern as well as help in analyzing their weak & strong areas. Get detailed Class 11th &12th Physics Notes to prepare for Boards as well as competitive exams like IIT JEE, NEET etc. eSaral helps the students in clearing and understanding each topic in a better way. eSaral is providing complete chapter-wise notes of Class 11th and 12th both for all subjects. Besides this, eSaral also offers NCERT Solutions, Previous year questions for JEE Main and Advance, Practice questions, Test Series for JEE Main, JEE Advanced and NEET, Important questions of Physics, Chemistry, Math, and Biology and many more. Download eSaral app for free study material and video tutorials.   Simulator   Previous Years AIEEE/JEE Mains Questions
Q. A man grows into a giant such that his linear dimensions increase by a factor of 9. Assuming that his density remains same, the stress in the leg will change by a factor of : (1) 81 ( 2)$\frac{1}{81}$ (3) 9 (4) $\frac{1}{9}$ [JEE-Main-2017]

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Sol. Stress $=\frac{\text { Force }}{\text { area }}=\frac{\mathrm{mg}}{\mathrm{A}}=\frac{\text { volume } \times \text { density } \times \mathrm{g}}{\text { Area }}$ Stress $=\frac{\mathrm{L}^{3} \rho \mathrm{g}}{\mathrm{L}^{2}}$ Stress $\propto \mathrm{L}$

Q. A solid sphere of radius r made of a soft material of bulk modulus K is surrounded by a liquid in a cylindrical container. A massless piston of area a floats on the surface of the liquid, covering entire cross section of cylindrical container. When a mass m is placed on the surface of the piston to compress the liquid, the fractional decrement in the radius of the sphere, $\left(\frac{\mathrm{dr}}{\mathrm{r}}\right)$, is : (1) $\frac{\mathrm{Ka}}{3 \mathrm{mg}}$ (2) $\frac{\mathrm{mg}}{3 \mathrm{Ka}}$ (3) $\frac{\mathrm{mg}}{\mathrm{Ka}}$ (4) $\frac{\mathrm{Ka}}{\mathrm{mg}}$ [JEE-Main-2018]

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Sol. $\left[\text { Bulk Modulus }=\frac{\text { volumetric stress }}{\text { volumetric strain }}\right]$ $\mathrm{K}=\frac{\mathrm{mg}}{\mathrm{a}\left(\frac{\mathrm{dV}}{\mathrm{V}}\right)}$ $\frac{\mathrm{d} \mathrm{V}}{\mathrm{V}}=\frac{\mathrm{mg}}{\mathrm{Ka}} \quad \ldots(\mathrm{i})$ volume of sphere $\rightarrow \mathrm{V}=\frac{4}{3} \pi \mathrm{R}^{3}$ Fractional change in volume $\frac{\mathrm{d} \mathrm{V}}{\mathrm{V}}=\frac{3 \mathrm{dr}}{\mathrm{r}} \ldots .$ (ii) $\mathrm{U}$ sing eq. (i) $\&(2) \frac{3 \mathrm{dr}}{\mathrm{r}}=\frac{\mathrm{mg}}{\mathrm{Ka}}$ $\frac{\mathrm{dr}}{\mathrm{r}}=\frac{\mathrm{mg}}{3 \mathrm{Ka}}$


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