A metallic ring of radius r and cross-sectional area A is fitted into a wooden circular disc of radius `R (R gt r)`. If the Young's modulus of the material of the ring is Y, the force with which the metal ring expands is

Options

A. `(AYR)/r`
B. `(AY(R-r))/r`
C. `(Y(R-r))/(Ar)`
D. `(YR)/(AR)`

Answer

B

Explanation

`E=F/A . L/l`
`F= (AE[2pi(R-r)])/(2pir) = (AY(R-r))/r`