Question

An elastic spring of unstretched length $L$ and force constant $K$ is stretched by a small length $x$. It is further stretched by another small length $y$. Work done during the second stretching is

• A. $\frac{ky}{2}(x+2y)$
• B. $\frac{k}{2}(x+2y)$
• C. $ky(x+2y)$
• D. $\frac{ky}{2}(2x+y)$

Answer 1

Answer: (D)

$\frac{ky}{2}(2x+y)$

$workdone=changeinPE=\frac{k}{2}({(x+y)}^2-x^2)=\frac{ky}{2}(2x+y)$