Read the text carefully and answer the questions:
There are many types of spring. Important among these are helical and spiral springs as shown in the figure. Usually, we assume that the springs are massless. Therefore, work done is stored in the spring the form of the elastic potential energy of the spring. Thus, the potential energy of a spring is the energy associated with the state of compression or expansion of an elastic spring.
a) When the potential energy of a spring may be considered as zero?