An elastic spring of unstretched length `L` and force constant `K` is stretched by amoun t `x` .It is further stretched by another length `y` The work done in the second streaching is

Options

A. `(1)/(2) Ky^(2)`
B. `(1)/(2) K(x^(2) + y^(2))`
C. `(1)/(2)Ky (2x + y)`
D. `(1)/(2) K(x + y)^(2)`

Answer

C

Explanation

`U = U_(2) - U_(1) = (1)/(2) K (x+y)^(2) - (1)/(2) Lx^(2)`