The work done in twisting a steel wire of length 25 cm and radius 2 mm through `4^(@)` will be `(eta= 8xx10^(10) N//m^(2)`

Options

A. 2.48 J
B. 3.1 J
C. 15. 47 J
D. 18.79 J

Answer

A

Explanation

`W= (1)/(2)C theta^(2)= (pi eta r^(4) theta^(2))/(4l) = (3.14 xx 8 xx 10^(10)xx(2xx10^(-3))^(4)xx(pi //4)^(2))/(4xx25xx10^(-2)) =2.48`J