# The Simple Pendulum

Is the simple pendulum considered to be an example of oscillatory motion or periodic motion or both?

## Answers and Replies

PeroK
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Is the simple pendulum considered to be an example of oscillatory motion or periodic motion or both?
Both!

ZapperZ
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Is the simple pendulum considered to be an example of oscillatory motion or periodic motion or both?

What do you know about the definitions of "oscillatory motion" and "periodic motion"?

Without us having the knowledge of what you already know, and without knowing those definitions and what a simple pendulum is, this will not be physics, but rather "stamp collecting" where we put something into a particular category without understanding why.

Suggestion: your posts should often consist more than just one single sentence, especially when you are new here and people still are not sure of your level of understanding.

Zz.

Mister T
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Is the simple pendulum considered to be an example of oscillatory motion or periodic motion or both?

In the introductory physics lessons on oscillatory motion the issue with the pendulum is that for small-amplitude oscillations the motion is approximately simple harmonic motion. But there are lots of examples of oscillatory motion that are not simple harmonic motion, and there are lots of examples of periodic motion that are not usually called oscillatory motion.

sophiecentaur
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there are lots of examples of periodic motion that are not usually called oscillatory motion.
I can't think of any. If you have 'motion' then something must be oscillating. You are seem to be querying the use of words but where is the distinction between the two terms that seems to be giving you a problem.
It's bad value for you to worry too much about the way terms are used. Just read a lot and come to your own conclusions whether people actually mean the same thing or if they are not particularly well informed. (It wouldn't be the first time, on the Internet. `0

PeroK
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I can't think of any.

An orbit, I would say, is periodic but not an oscillation.

sophiecentaur
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An orbit, I would say, is periodic but not an oscillation.
Can't it be regarded as oscillation along two axes?

Mister T
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Can't it be regarded as oscillation along two axes?

Sure it can. It's just unusual to refer to that kind of periodic motion as oscillatory motion.

PeroK
sophiecentaur
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Sure it can. It's just unusual to refer to that kind of periodic motion as oscillatory motion.
Which all goes to show how threads about terminology and classification tend not to get us very far. If you hang up a pendulum and push it in a direction, slightly away from the centre, you surely can't describe its motion as being fundamentally different from when you just let it go.
The definitions of either term seem to contain and certainly don't exclude the other. Not something to worry about too much.

Merlin3189
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If you have 'motion' then something must be oscillating.
Uniform motion (straight line or rest) or trajectories that don’t form closed orbits would be examples of “not oscillatory” motion.

As for “oscillatory” vs. “periodic,” I’d argue that there does seem to be a useful difference, at least in the common usage that I am familiar with. Oscillatory means anything that “swings” between states around a mean. This includes a simple pendulum, which is in periodic motion. However, people also talk about other oscillatory systems that are clearly aperodic, such as a damped oscillator or maybe a flag flapping in the wind or even El Niño.

sophiecentaur
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I don't feel that strongly abut this. I would say that a well written description of any phenomenon would not hang on the choice of either word in particular. But your point about regularity is well made and could distinguish between the two terms.

Merlin3189