A mass on a spring is a common physics experiment that demonstrates the principles of harmonic motion. When a mass is attached to a spring and pulled or compressed, it will oscillate back and forth around an equilibrium position. The spring exerts a restoring force proportional to its displacement, following Hooke's Law, which states that the force is equal to the spring constant multiplied by the distance stretched or compressed. The motion of the mass can be described as periodic, meaning it repeats over time. The frequency and amplitude of the oscillation depend on the mass and the spring constant. This system is often used to illustrate concepts in mechanics and vibrations.