Question

A wire of radius $1mm$ is bent in the form of a circle of radius $10cm$. The bending moment will be $(Y=2\times {10}^{11}N/m^2)$

• A. 3.14 N/m
• B. 6.28 N/m
• C. 1.57 N/m
• D. 15.7 N/m

Answer 1

Answer: (C)

1.57 N/m

Bending Moment $C=\frac{Y{I}_G}{R}$
where $Y=2\times {10}^{11}N/m^2$
$R=10cm=0.1m$
$I_G=\frac{\pi R^4}{4}=\frac{\pi {0.1}^4}{4}=7.85\times {10}^{-5}{m}^4$
Put these in the expression for $C$,
$C=1.57N/m$