question_answer

The elastic limit of brass is 379 MPa. What should be the minimum diameter of a brass rod if it is to support a 400 N load without exceeding its elastic limit?                                                 [JEE Main 10-4-2019 Afternoon]

A)  1.16 mm         

B)       0.90 mm C)  1.36 mm          D)       1.00 mm Correct Answer: A Solution : [a] \[\frac{F}{A}=stress\]

\[\frac{400\times 4}{\pi {{d}^{2}}}=379\times {{10}^{6}}\]

\[{{d}^{2}}=\frac{1600}{\pi \times 379\times {{10}^{6}}}=1.34\times {{10}^{-6}}\]

\[d=\sqrt{1.34}\times {{10}^{-3}}=1.15\times {{10}^{-3}}m\]