What kind of energy is stored in a spring?

The energy stored in a spring when it is compressed or stretched is known as elastic potential energy. This type of energy arises from the deformation of the spring, which occurs when it is either pulled apart or pushed together. According to Hooke's Law, the amount of elastic potential energy stored in the spring is proportional to the distance it is stretched or compressed from its equilibrium position. When the spring is released, the elastic potential energy converts back into kinetic energy, allowing the spring to return to its original shape.

In contrast, other forms of energy do not apply as directly to a spring. Kinetic energy refers to the energy of motion, which is relevant when an object is moving but does not describe the energy stored in a static deformed spring. Gravitational potential energy pertains to an object's position relative to a gravitational field, such as a rock on a hill, and does not involve springs. Thermal energy is related to the temperature of an object and the motion of its particles, but it is not a descriptor of the energy stored in springs.

Therefore, elastic potential energy accurately describes the energy stored in a spring when it is deformed.