NA 1. Simple Harmonic Motion

LEARNING TARGETS

State examples of simple harmonic motion (SHM)

Define the terms displacement, amplitude, frequency and period

Describe how the displacement, speed, kinetic energy and potential energy of an object changes over time as it undergoes simple harmonic motion

Simple harmonic is motion is motion in which an object moves back and forth around a rest position. 

When the object is displaced from the rest position a force acts to return it there. For motion to be simple harmonic, the size of the force must be DIRECTLY proportional to the displacement (this means if you double the displacement you double the force) and it must act towards the rest position.

Examples of simple harmonic motion include a mass oscillating on a spring, a swing or pendulum, car or bicycle suspension systems and a trampoline after somebody has jumped from it.

Click on the picture below

Some terms that you need to know the meaning of:

Displacement: The distance of an object from the rest position at a particular point in time - measured in metres, cm or mm

Period: The time taken for one complete oscillation (or cycle) - measured in seconds

Frequency: The number of oscillations (or cycles) in 1 second - measured in Hertz

Amplitude: The maximum displacement of an object from the rest position - measured in metres, cm or mm.

We can analyze the motion of an object that is undergoing simple harmonic motion (using apparatus like a motion sensor) to give graphs like the two below. Notice that the object is moving at its fastest speed (or velocity) when it is passing through the rest position (zero displacement)

[A positive displacement means the object is above the rest position, a negative displacement is below. A positive velocity means the object is moving upwards, a negative velocity means it is moving downwards]

You do not need to know everything that is shown in this video!!! The key things to understand are in the first 3 minutes

Lab Time!!