Q. Forces of 100 N each are applied in opposite directions on the upper and lower faces of a cube of side 20 cm. The upper face is shifted parallel to itself by 0.25 cm. If the side of the cube were 10 cm, then the displacement would be
A) 0.25 cm
B) 0.5 cm
C) 0.75 cm
D) 1 cm
Explanation
(b) $\eta\ = \ \frac{Fl}{A\Delta l} = \ \frac{Fl}{l^{2}\Delta l} = \ \frac{F}{l\ \Delta l}\ or\ \Delta l\ \propto \frac{1}{l}$
If $l$ is halved, then $\mathrm{\Delta}l$ is doubled.
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.