Simple Harmonic Motion Lab Experiment (Pendulum / Spring)

Think of the soothing tick-tock of a grandfather clock or the bounce of a car suspension. These are everyday examples of Simple Harmonic Motion, a fundamental concept in physics where an object moves back and forth around a central equilibrium point.

In a physics lab, we demystify this rhythmic dance using two classic setups: a simple pendulum and a mass hanging from a spring. When you displace either system from its resting position, a restoring force pulls it back. The defining rule of simple harmonic motion is that this restoring force is directly proportional to the displacement—the further you pull it, the harder it pulls back.

Let’s look at what controls the tempo, known as the period of oscillation. With a pendulum, a curious truth emerges: changing the mass of the bob does not change the time it takes to complete one full swing. Only the length of the string and the pull of gravity dictate the period. Conversely, in a mass-spring system, mass matters immensely. A heavier weight bounces slower, while a stiffer spring snaps back faster.

Throughout both experiments, we witness a flawless trade-off between kinetic and potential energy. At the peak of a swing or stretch, velocity is zero and potential energy is at its maximum. As the object rushes through the center equilibrium point, potential energy drops to zero, and kinetic energy peaks. Testing these variables in a lab helps us understand everything from quantum mechanics to how to build earthquake-resistant skyscrapers.