A and B are two wire. The radius of A is twice that of B. If they are stretched by the same load, then the stress on B is

Options

A. equal to that of A
B. two times that of A
C. four times that of A
D. half that of A

Answer

c

Explanation

stress `= (F)/(S)`
Let r be the radius of B
For `A, (F)/(pi (2 r)^(2)) = (F)/(pi (4 r^(2)))`
For B, stress `= (F)/(pi r^(2))`
`:. (F)/(pi r^(2)) = 4 [(F)/(pi r^(2))]`
stress on B = 4 (stress on A)