## Summary

Whether it's a pendulum, a mass on a spring or an electrical oscillator, an oscillating system can be described in terms of energy changing from one form to another.

## Get the basics

#### Energy changes in a pendulum

When a pendulum is released, E_{P} is converted to E_{K} as it swings to the lowest point. On the way back up the other side E_{K} is converted back to E_{P}. E_{P} is again converted to E_{K} and back to E_{P} on the swing back.

Energy is constantly changing from E_{P} to E_{K} and back but the total is always the same.

#### Energy changes in a mass on a spring

It requires a force to both stretch and compress a spring. As a mass oscillates on a spring, elastic potential energy is stored when the spring is both stretched and compressed. In between, the mass has kinetic energy.

## Stretch for 7

#### Energy changes in a mass on a spring - this time with extra gravity!

A mass oscillating on a spring in a gravitational field is complicated by the fact that there are two components of potential energy, gravitational and elastic.

NB: The overall oscillating energy graph looks identical as the equilibrium position shifts, but oscillations still occur symmetrically around this.