# What is the difference between SHM,oscillation and vibratory motion?

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What is the difference between SHM ,oscillation and vibratory motion?

How many types of oscillations/vibratory motion are there?
If shm is one type of oscillation the what are the other types?

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3. ### Naty1

Different people probably use the terms a bit differently....

Simple harmonic motion is typically considered to be a type of periodic motion...and it may decay or not as used in everyday language.

Oscillation is a more general term,....

oops: I just checked Wikipedia...and they refer to an oscillating weight on a spring and as
simple harmonic motion.....and as 'oscillations' in another article....

Wiki says:
I never heard of it used that way.

Aboard a boat, one refers to 'engine vibration' meaning the engine is missing, maybe a mount is loose, or maybe the drive train is out of alignment...as in a bent propeller.
I'd love to know where the 'equilibrium point' is in such a situation.

So Ill change my opening line to 'there is no consistency' ....

4. ### Studiot

OK.

Oscillation and vibration mean basically the same thing,

However

The term oscillation is usually reserved for periodic motion in which the whole body particpates as a rigid body, eg the oscillation of a mass on a spring or the oscillation of a pendulum. In essence the whole of the body is doing the same motion.

The term vibration usually refers to some kind of motion where one part of the body goes one way and another part goes another way. This usually means flexural vibration and larger objects such as buildings or bridges or electric cables. You can here cables vibrating in the wind where they are acting like guitar strings and different parts of the string are exefcuting different motions.

Simple harmonic motion means that there is no loss of energy to for instance friction so once set going the oscillation will never cease. It is characterised by a sinusoidal displacement graph.
Damped simple harmonic motion introduces some form of energy dissipation whilst maintaining the sinusoidal form.

You should also note that wave motion is different again.

Oscillations, vibrations and SHM refer to one one single vibrating or oscillating entity.

Wave motion occurs when there are many similar oscillators that have some form of coupling to transfer the motion or energy from one to the other.

Last edited: Jan 3, 2013
5. ### BruceW

3,529
AFAIK vibration and oscillation are general terms to describe behaviour qualitatively. And SHM means something more specific (mathematically) $\ddot{x}=-kx$