A spring of spring constant `5xx10^(3) N//m` is stretched by 4 cm from its unstreched of position. Then the work required to stretch it further by 4 cm is

Options

A. 6 N
B. 12 N
C. 18 N
D. 3 N

Answer

B

Explanation

For a spring, the `P.E. U_(1)=(1)/(2)Kx_(1)^(2) and U_(2)=(1)/(2)Kx_(2)^(2)`
`therefore` The work done,
`W=(1)/(2)K(x_(2)^(2)-x_(1)^(2))`
`=(1)/(2)xx5xx10^(3)[(8xx10^(-2))^(2)-(4xx10^(-2))^(2)]`
`therefore W= (5)/(2)xx10^(3)xx48xx10^(-4)=12 N`