Q. A rectangular bar 2 cm in breadth and 1 cm in depth and 100 cm in length is supported at its ends and a load of 2 kg is applied at its middle. If Young’s modulus of the material of the bar is $20\ \times 10^{11}dyne\ cm^{- 2},$ the depression in the bar is
A) 0.2450 cm
B) 0.3675
C) 0.1225 cm
D) 0.9800 cm
Explanation
(c) Here, $w = 2 \times 1000 \times 980\ dyne;l = 100\ cm,\ b = 2\ cm\ ,\ d = 1\ cm,\ Y = 20 \times 10^{11}dyne\ cm^{- 2}$,
Now, $\delta = \ \frac{wl^{3}}{4Ybd^{3}} = \ \frac{(2 \times 1000 \times 980) \times (100)^{3}}{4 \times \left( 20 \times 10^{11} \right) \times 2 \times (1)^{3}}$
= 0.1225 cm.
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.