Tell me more ×
Physics Stack Exchange is a question and answer site for active researchers, academics and students of physics. It's 100% free, no registration required.
up vote 2 down vote favorite

In diagrams that contain the dashpot symbol, sometimes the mass is attached to the "interior" end of the dashpot, other times the mass is attached to the "base" end.

For example, consider the following diagram (please ignore the equations):

enter image description here

Does it make any difference if the dashpot symbol in the above figure is reflected in the vertical line? If not, which is the conventional orientation to draw the dashpot in?

Thanks.

share|improve this question
By dashpot, do you mean the symbol below "C"? All you need to solve the problem is the differential equation, i.e the term proportional to the velocity. The picture is irrelevant. – Antillar Maximus Sep 1 '12 at 14:18
@AntillarMaximus Yes I mean that symbol. Oh I'm not trying to solve the problem (the picture was googled up). My question is about the symbol because I've seen it both ways in the notes I was given and I want to know what's the essential difference between the two differnt representations (orientated two different ways). – Ryan Sep 1 '12 at 14:25
You should look for the terms "driven" ,"damped" in the notes. This is what decides the behavior of your oscillator. No matter how the picture is, if your notes say "damped" you will have one form of the equation, if it says "driven" you will have the other form. Are you studying R-C oscillators? – Antillar Maximus Sep 1 '12 at 14:34
1  
@AntillarMaximus I am merely asking about the symbol! Why is it sometimes directed one way and other times directed in the opposite direction? Ignore any perceived physics problem! – Ryan Sep 1 '12 at 14:59
It depends on the whim of the author I suppose. – Antillar Maximus Sep 1 '12 at 15:59

1 Answer

up vote 1 down vote accepted

The direction is absolutely irrelevant, it can be either way. Just imagine that damper, a kind of piston and how you stretch and contract it. Thus you should intuitively feel why the orientation doesn't matter. Below is a bit more rigorous explanation:

The power required by an external force to move a damper doesn't depend on the damper's orientation, only on the relative speed of its parts. Or probably the relative position of it's parts. And distance and relative speed don't depend on the orientation, that's just the basic property of our usual spacetime.

share|improve this answer
Yes I didn't think the orientation would be relevant to the damping problems, but I sincerely thought that there would be a standard convention to draw these things. Like the "interior" end always facing the mass, or or "base" end always facing the mass. – Ryan Sep 2 '12 at 9:09

Your Answer

 
discard

By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.