### Harmonic Motion

Each list begins with basic conceptual vocabulary you need to know for MCAT questions and proceeds to advanced terms that might appear in context in MCAT passages. The terms are links to Wikipedia articles.

**Simple harmonic motion**

Simple harmonic motion is the motion of a simple oscillator.

**Pendulum**

A pendulum is an object that is attached to a pivot point so it can swing freely.

**Amplitude**

The amplitude is a nonnegative scalar measure of a wave's magnitude of oscillation, the magnitude of the maximum disturbance in the medium during one wave cycle.

**Frequency**

Frequency is the measurement of the number of occurrences of a repeated event per unit of time.

**Spring**

A spring is a flexible elastic object used to store mechanical energy usually made out of hardened steel.

**Bob**

A bob is the weight on the end of a pendulum.

**Oscillation**

Oscillation is the variation of some measure about a central value (often a point of equilibrium) or between two or more different states.

**Harmonic oscillator**

A harmonic oscillator is a system which, when displaced from its equilibrium position, experiences a restoring force proportional to the displacement.

**Hertz**

The hertz is the SI unit of frequency. Its base unit is the cycle per second.

**Damping**

Damping is any effect that tends to reduce the amplitude of oscillations of an oscillatory system.

**Periodic function**

A periodic function is a function that repeats its values after some definite period has been added to its independent variable.

**Periodicity**

Periodicity is the quality of occurring at regular intervals or periods in time or space.

**Phase**

The phase of an oscillation or wave is the fraction of a cycle corresponding to an offset in the displacement from a specified reference point at time t = 0.

**Vibration**

Vibration refers to mechanical oscillations about an equilibrium point. The oscillations may be periodic such as the motion of a pendulum or random such as the movement of a tire on a gravel road.

**Resonance**

Resonance is the tendency of a system to oscillate at maximum amplitude at a certain frequency.

**Small-angle approximation**

The small-angle approximation is a useful simplification of the laws of trigonometry which is only approximately true for finite angles, but correct in the limit as the angle approaches zero.

**Isochronous**

Isochronous means having an equal time difference or occurring simultaneously.

**Double pendulum**

A double pendulum is a system of two simple pendulums on a common mounting which move in anti-phase.

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