A metal ring of initial radius r and cross-sectional area A is fitted onto a wooden disc of radius R > r. If Youngs modules of metal is Y then tension in the ring is

Options

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

Answer

B

Explanation

As we know `Y= (FL)/(A xx Delta L)`
`F= (YA xx Delta L)/(L) = (YA (2pi R- 2pi r))/(2pi r)`
`therefore F= YA((R-r)/(r ))`