Work done required to stretch the spring from its natural length of cm to a length of cm is J.

(a)

Work done in moving the object from to  is .

Here , and cm m.

From the Hookes law , .

Substitute , , and in .

Therefore, spring constant N/m.

Find the work done to stretch a spring from cm to cm.

Force required in moving an object to a distance of m is .

Natural length of the spring is cm.

Now calculate work done to stretch a spring of length of cm to cm from its natural length.

Here  and .

Work done is

J.

Work done required is J. 

(b)

From the Hookes law , .

Force kept on spring is N.

We have  spring constant N/m.

Substitute and in .

.

Force of  N kept the spring stretched beyond the natural length is .

(a) Work done required is J.

(b) Force of  N kept the spring stretched beyond the natural length is .