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What variables affect the damping of a spring executing simple harmonic motion?

What are the independent variables, and what variables would need to be controlled in an experiment?

I'm attempting to complete an investigation where I measure the decrease in amplitude of a damped spring, and to prove the relationship between variables in the motion.

Thanks!

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An interesting paper partially addressing your question: prd.aps.org/abstract/PRD/v42/i8/p2437_1 –  nibot Apr 11 '11 at 17:49
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up vote 3 down vote accepted

You should already be familiar with damping. It simply refers to the fact that if you set a spring going, it eventually stops.

The wikipedia article should cover most of what you want to know.

Any particular spring may be damped for all sorts of reasons. Any way the spring can lose energy contributes to damping, so it could be lost internally to heat due to stressing the material, or externally to heat via friction, or externally to an electromagnetic field, to some sort of mechanical dashpot, etc.

If you were designing an experiment to study damping, you could be interested in a number of different particular things. You will have to make your own choice about what the most interesting thing to study is. For example, would you like measure the damping ratio? The overall magnitude of the damping effect? The time it takes your spring to reduce its amplitude to 1/2 its previous value?

If you have a particular effect picked out, do you want to know how it depends on the load on the spring, or the material of the spring, or whether the spring is in a vacuum, etc. There are many possible things to study, so your question has no definite answer. I'm sure you can find something particular you find worthwhile.

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In regards to an experiment, it will likely be investigating damping considering only frictional forces. I'm intending to measure the gradual decrease in the amplitude of a spring. It sounds like the dampening ratio will be relevant in that scenario. I've read the wiki page, but I'm afraid I don't really understand it. Could you explain the concept in simpler terms? –  MathsStudent Apr 11 '11 at 7:50
    
@Maths The damping ratio simply tells you how close something is to being critically damped. Critically damped is the least amount of damping that still keeps the spring from oscillating back and forth about the equilibrium. –  Mark Eichenlaub Apr 11 '11 at 7:55
    
Okay, so what variables would need to be tested, and what variables would be controlled in the scenario outlined? –  MathsStudent Apr 11 '11 at 8:09
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@Maths I think I've done enough for now. If you understand what controls and independent and dependent variables are, you should be able to take it from here. –  Mark Eichenlaub Apr 11 '11 at 8:12
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@MathsStudent: Mark has given you a lot of help here. It seems to me that the underlying problem is that you don't understand how to design an experiment. We can't really explain that to you here in the level of detail it sounds like you need. I'd suggest that you seek help directly from your teacher. –  David Z Apr 11 '11 at 8:45
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