# What is the difference between SHM and HM ?

1. Jun 5, 2008

### linuxpie

What is the difference between Simple Harmonic Motion and Harmonic Motion ?
and How do we define the motion of a system is SHM ?

Thank you !

2. Jun 5, 2008

### Andy Resnick

Sometimes they are used interchangably. SHM is usually taken to mean purely sinusoidal behavior. "harmonic motion" could simply mean regularly repeating behavior, but could consist of multiple frequencies (fundamental, overtones, undertones, additional fundamental excitations, etc)

3. Jun 5, 2008

### tiny-tim

Welcome to PF!

Hi linuxpie ! Welcome to PF!

See http://en.wikipedia.org/wiki/Complex_harmonic_motion:
SHM is where the restoring force is proportional to the displacement (or look up wikipedia! ).

4. Jun 5, 2008

### tonyh

My understanding is that 'harmonic' is synonymous to periodic, and the 'simple' means that the displacement (from the origin) is a sinusodal function of time - i.e., a mathematically simple function. For example x(t)=Acos(wt+$$\phi$$), where A,w and $$\phi$$ are constants. This is equivalent to the definition that tiny-tim gave above.

5. Jun 6, 2008

### linuxpie

Thank you all !