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Theory for Coefficient of drag


Endercreeper01

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No, that's nonsense again. What are you going to divide by? Inches? mm? or light years? All are perfectly valid units of length, why is any one of them more special than the others?

 

The laws of physics are actually independent of units and coordinate systems. There is no good reason that drag should be the one exception to this.

Edited by Bignose
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You would only divide by the number if they both used the same units for measuring length.

So, if I measured in inches and you measured in mm, then you wouldn't divide? I've never heard of a theory dependent upon two people using the same ruler.

 

And you'd still have your drag coefficient having a unit of length if everybody did use the same ruler. That still isn't fixed. The point being, that your equation for a dimensionless number shouldn't have dimensions on one side of the equation. You need an equation that all the dimensions cancel out on both sides.

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I can criticize an idea that has the wrong units without knowing all the details of how it ended up with the wrong units.

 

Your dimensionless drag coefficient has dimension of length. End of story. Something is wrong. Having the correct units doesn't mean the formula is correct, but it is a good first check.

 

This is like changing F = ma to F = mal. You just can't do it. The units on the left hand side and the right hand side have to match. There is no formula in physics anywhere where this isn't true.

 

Also, I want to say, I don't think it is fair for you to criticize me for 'not understanding' when I've pointed out where the misunderstandings are, I ask pointed questions about them, and you do nothing but hand wave them away. A significant source of the misunderstanding is the poor communication and presentation of your idea. So, yes, I don't understand because you haven't made it understandable.

Edited by Bignose
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The thing is, D is not dimensionless and has units of 1/l. Therefore, when you have l in the equation, then the 1/l unit and the l unit cancels out. This is because the definition of D is that it is the form drag coefficient it would have if it was a rectangular prism divided by the length, which makes it the form drag coefficient it would have if it was a cube, but with units of 1/l. When you multiply by l, the 1/l and l units cancel out, giving you no dimensions.

So basically, Dl is the form drag coefficient it would have if it was a rectangular prism with the same length.

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k, fine, whatever. Another handwaving dismissal of my criticism by just -- for no reason other than it fixes this immediate issue -- the units of the drag coefficient are now changed. No real justification. No answer of how it now changes all the other previous equations to having wrong dimensions. Just suddenly, D has units of 1/length.

 

I'm done. This hand waving slapdash of each issue is not real science and very uninteresting.

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D is the drag coefficient it would have if it was a rectangular prism divided by l! What part don't you understand?!

When you have Dl, it becomes the drag coefficient it would have if it was a rectangular prism with that same length! What is so hard to understand about that?!

This is just pissing me off! D Now has units of 1/l because of what I said!

 

the definition of D is that it is the form drag coefficient it would have if it was a rectangular prism divided by the length, which makes it the form drag coefficient it would have if it was a cube, but with units of 1/l. When you multiply by l, the 1/l and l units cancel out, giving you no dimensions.

 

 

It isn't just all of a sudden! I told you why it was in units of 1/l !

Seriously, listen to what I am saying.


And now, you will just consider this "trolling".

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