Suppose that 5 Joules of work is needed to stretch a spring from its natural length of 15 cm to a length of 36 cm.

a) How much work is needed to stretch the spring from 16 cm to 30 cm?

W = Så f(x)dx, where ƒ(x) = ¯‚ a :

W =

=a=0₁

and b

=

b) How far (in meters) beyond its natural length would a force of 40 N keep the spring stretched? m.