A spring has an unstretched length of 10cm. When it is hung with a load of 80g attached, the stretched length is 28 cm. Assuming that the extension of the spring is proportional to the load:
(i) draw a graph of extension E against load L and find its equation.
(ii) find the load required to extend the spring to a length of 20 cm.
This particular spring passes its elastic limit when it is stretched to four times its original length.
(iv) Find the load which would cause this to happen.