Simple Harmonic Motion: What is Superposition of SHM?

[Zubair Ahmad]

What does superposition of SHM means physically.. I mean how is it that two shms superpose on same system?

 

[BvU]

A vibrating string, for instance: points on the string can take part in a whole spectrum of frequencies

 

[sophiecentaur]

What does superposition of SHM means physically.. I mean how is it that two shms superpose on same system?

Take a specific example. A string with a low frequency sinusoidal wave on it (long wavelength waves passing along it from one end to the other). Now vibrate the string with an additional low amplitude high frequency wave. Those short waves will be 'superimposed' on the larger long waves and progress along the string. If the string behaves linearly (i.e. tension at any instant is proportional to the stretch in the string) the resulting motion of any part of the string will be the result of the two waves, independently. It will consist of just two sine waves superimposed on each other. (Or for any combination of waves.)
Same for em waves, sound waves etc. etc.