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# Investigating viscous damping

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1. Hi all,
I am having a personal investigation on the effect of viscous damping on resonance. This is done by having a mass oscillating vertically in a viscous liquid(water). By changing temperature and mass, i can record some results.

One of my research question is:
How does the temperature affect the amplitude and corresponding frequency for a resonance motion?

From my experimental results I have used temperature from 25ºC to 60ºC with 5ºC intervals. I found that the amplitude stays roughly the same on different temperature however the resonance frequency increases as temperature increases. I know it is to do with the fact that the water becomes less viscous as temperature increases which means particles gain more energy and move about more. But why is that the amplitude stays the same and can Stoke's Law help to explain my findings?

Thanks
2. (Original post by MarcoWrong)
Hi all,
I am having a personal investigation on the effect of viscous damping on resonance. This is done by having a mass oscillating vertically in a viscous liquid(water). By changing temperature and mass, i can record some results.

One of my research question is:
How does the temperature affect the amplitude and corresponding frequency for a resonance motion?

From my experimental results I have used temperature from 25ºC to 60ºC with 5ºC intervals. I found that the amplitude stays roughly the same on different temperature however the resonance frequency increases as temperature increases. I know it is to do with the fact that the water becomes less viscous as temperature increases which means particles gain more energy and move about more. But why is that the amplitude stays the same and can Stoke's Law help to explain my findings?

Thanks
3. (Original post by NNB_Herath)
18 but why?
4. Hmm, now while im no expert in fluid dynamics, but i do think that your amplitude must change due to a change in temperature (and therefore viscosity)...
So you have:

Now, as all other variables are control variables, i.e the fluid viscosity is the only thing that changes with temperature.

As (temperature increase means fluid viscosity decrease)

As decreases, decreases also and so the mass should encounter less force. This lacking of force would mean the mass should therefore move further before being slowed by the counterforce, and so therefore should have a greater amplitude (if thats what you mean).

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