Q. To break a wire of one metre length, minimum $40\ kg\ wt$, is required. Then the wire of the same material of double radius and $6\ m$ length will require breaking weight
A) $80\ kg$-$wt$
B) $240\ kg$-$wt$
C) $200\ kg$-$wt$
D) $160\ kg$-$wt$
Explanation
(d) Breaking force = Breaking stress $\times$ Area of cross section of wire
$\therefore$ Breaking force $\propto r^{2}$ (Breaking stress is constant)
If radius becomes doubled then breaking force will become 4 times $i.e.\ 40 \times 4 = 160\ kg\ wt$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.