A load $W$ produces an extension of $1mm$ in a thread of radius $r.$ Now if the load is made $4W$ and radius is made $2r$ all other things remaining same, the extension will become..... $mm$
A$4$
B$16$
C$1$
D$0.25$
Medium
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C$1$
c (c) $l = \frac{{FL}}{{AY}}\therefore l \propto \frac{F}{{{r^2}}}$
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