# A force of 1200 N compresses a spring from its natural length of 18 cm to a length of 16 cm. How much work is done in compressing it from 16 cm to 14 cm?

$\begin{array}{1 1}3600N.cm\\3000N.cm\\3500N.cm\\2500N.cm\end{array}$

We must work out the spring constant first (we will work in cm)
$F=kx$
So $1200 =k(2)$
So $k=600N/cm$
So in this case,
$F=600x$
Now the work done is given by :
Work =$\int_2^4 600xdx$
$\qquad=\bigg[300x^2\bigg]_2^4$
$\qquad=3600N.cm$