A high-capacity shock absorber in an industrial elevator safety system uses a heavy-duty spring. During a test, a compressive force of 1.6 kN1.6\text{ kN}1.6 kN is applied to the spring, causing it to compress elastically by 4.5 cm.
What is the elastic potential energy stored in the spring?
3.6 J3.6\text{ J}3.6 J
36 J36\text{ J}36 J
72 J72\text{ J}72 J
3600 J3600\text{ J}3600 J
