Posted by DAN on .
A spring with spring constant k=100 (N/m) is at its equilibrium length.
a) How much elastic potential energy is stored in the spring?
b) The same spring is stretched so that it is 6.0 cm longer than its equilibrium length. How much elastic potential energy is stored in the spring now?
c) A different spring with spring constant four times larger than in part (a) is compressed so that it is 2.0 cm shorter than its equilibrium length. How much elastic potential energy is stored in this spring?

Physics 
drwls,
a) zero
b) (1/2) k X^2, where X = 0.06 m
c) In this case, X is 1/3 of the previous example, and k is 4 times greater. Use the same formula and see what you get.