A certain spring that obeys Hook's law is stretched by an external agent. The work done in stretching the spring by `10 cm is 4 J` . How much additional work is required to stretch the spring an additional `10 cm`?

Explanation

Here, `W=4J,x=10cm,=10^(-1)m`
As ` W=(1)/(2)Kx^(2)`
`:.K=(2W)/(x^(2))=(2xx4)/((10^(-1))^(2))=800N//m`
Total work done in stretching the spring through
`x^(')=20cm` is `(1)/(2)Kx'^(2)=(1)/(2)xx800((20)/(100))^(2)=16J`
Extra work required `=16J-4J=12J`