# Definitions,
equations and graphs

##
Definition of Simple
Harmonic Motion
(SHM):
LO (d)

A motion where the acceleration a of an object
is always directed towards a fixed point ( the
equilibrium position O ) and proportional to its displacement x from the fixed point
is said to be be simple harmonic.

Defining equation of SHM

a = - ω^{2} x

Observe from
the model or the animation, suggest the reason for the negative
sign.

The negative
sign means a is always directed towards the equilibrium point
while x is pointing away from equilibrium point O.

In other words a and x are in the opposite direction.

## Model:

http://dl.dropboxusercontent.com/u/44365627/lookangEJSworkspace/export/ejss_model_SHM07/SHM07_Simulation.xhtml