What energy is stored in a stretched or compressed object, such as a spring?

• A. Kinetic Energy
• B. Momentum
• C. Elastic Potential Energy
• D. Conservation of Energy

Answer: (C)

Elastic potential energy is the energy stored when an object is stretched or compressed. When you deform a spring, you do work against its restoring force, and that work becomes stored as elastic potential energy in the spring. The amount stored grows with how stiff the spring and how far you deform it, described by U = 1/2 k x^2 for an ideal spring. When the deformation is released, that stored energy can convert into kinetic energy as the spring moves back toward its natural length. This distinguishes it from kinetic energy, which is energy of motion, and from momentum, which is a property of moving objects; conservation of energy is the principle describing how energy changes form, not a type of energy itself.