Equation for power required to overcome drag

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    Drag Power
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Discussion Overview

The discussion revolves around the equation for calculating the power required to overcome drag when an object moves through a fluid. Participants explore the validity of a specific equation referenced from a website, questioning its assumptions and interpretations.

Discussion Character

  • Debate/contested
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • Some participants assert that the equation presented in the linked source is correct, emphasizing that it calculates drag power as the product of drag force and fluid speed relative to the object.
  • Others express uncertainty about the equation's validity, questioning the assumptions behind it and whether the speed variable is defined correctly.
  • A participant recalls a previous disagreement regarding the interpretation of speed in the equation, suggesting it was thought to be the object's speed relative to the ground rather than the fluid speed.
  • There are references to moderation actions and previous threads, indicating ongoing concerns about the discussion's direction and the participants' posting history.
  • Some participants mention the practical applications of the equation, such as in wind turbine design and vehicle performance calculations.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the correctness of the equation. Multiple competing views remain regarding its interpretation and the assumptions that underlie it.

Contextual Notes

Participants highlight the need for clarity on the assumptions behind the equation, indicating that there may be unresolved aspects related to its application and interpretation.

electrodacus
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Here is the link to the equation I consider to be correct https://scienceworld.wolfram.com/physics/DragPower.html
Is anyone disagreeing with that and if so can you provide a link or screenshot from a proper textbook ?
The v in that equation is defined as speed of the fluid relative to the body.
 
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electrodacus said:
Here is the link to the equation I consider to be correct https://scienceworld.wolfram.com/physics/DragPower.html
Is anyone disagreeing with that and if so can you provide a link or screenshot from a proper textbook ?
The v in that equation is defined as speed of the fluid relative to the body.
It is the drag force multiplied by the speed which makes it the drag power. If drag power is what you're looking for, it is correct.
 
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Thread closed temporarily for Moderation...
 
electrodacus said:
Here is the link to the equation I consider to be correct https://scienceworld.wolfram.com/physics/DragPower.html
Is anyone disagreeing with that and if so can you provide a link or screenshot from a proper textbook ?
The v in that equation is defined as speed of the fluid relative to the body.

Thread reopened, sort of...

Is this related to your two previously closed threads, and your temporary vacation from PF?
 
berkeman said:
Thread reopened, sort of...

Is this related to your two previously closed threads, and your temporary vacation from PF?

The question is as simple as stated. I asked if that is the correct equation ?
I think it is but I can always be wrong.
 
electrodacus said:
The question is as simple as stated. I asked if that is the correct equation ?
I think it is but I can always be wrong.
No. Just like a traffic cop stopping a car for rolling through a red light, the Mentors monitor your posting history and use it to Moderate future posts. We do not allow restarting locked threads, even if you initially try to hide your motives.

electrodacus said:
Is anyone disagreeing with that and if so can you provide a link or screenshot from a proper textbook ?
Under what assumptions? What are the assumptions behind that web page formula?
 
berkeman said:
Under what assumptions? What are the assumptions behind that web page formula?
Not everybody seems to agree with that equation.
Maybe there is something that I'm missing or not understanding so I want to make sure that is the correct equation if I want to calculate the power needed by an object to overcome drag (any object traveling through a fluid).
The discussion on this thread will not go any further than confirming that equation is correct.
 
Last edited by a moderator:
electrodacus said:
Not everybody seems to agree with that equation.
Who are the people who don't agree and what do they say? We can't have a proxy debate with people who aren't in the thread and are not cited.
The discussion on this thread will not go any further than confirming that equation is correct.
The answer was given in post #2.
 
russ_watters said:
Who are the people who don't agree and what do they say? We can't have a proxy debate with people who aren't in the thread and are not cited.

The answer was given in post #2.

Yes post #2 has provided the answer that I consider to be correct thus I used the Like button for that post.
Even yourself disagreed with this equation in the past.
The claim if I remember correctly was that
- speed in that equation was the object/vehicle speed relative to ground times drag force
- while I was claiming that speed is the fluid speed relative to the object/vehicle.
 
  • #10
electrodacus said:
Even yourself disagreed with this equation in the past.
The claim if I remember correctly was that
- speed in that equation was the object/vehicle speed relative to ground times drag force
Neither of those is true.

So, this is a continuation of your prior threads on DWFTTW, right? If not, where are we going from here?
 
  • #11
electrodacus said:
Yes post #2 has provided the answer that I consider to be correct thus I used the Like button for that post.
Even yourself disagreed with this equation in the past.
The claim if I remember correctly was that
- speed in that equation was the object/vehicle speed relative to ground times drag force
- while I was claiming that speed is the fluid speed relative to the object/vehicle.
https://www.google.com/url?sa=i&url...ved=0CA8QjRxqFwoTCIi7janK9fsCFQAAAAAdAAAAABAH
 
  • #12
It gives me an error as video unavailable.
 
  • #13
russ_watters said:
Neither of those is true.

So, this is a continuation of your prior threads on DWFTTW, right? If not, where are we going from here?
This is strictly about this equation. It is one of the more important equations in physics in my opinion.

You will need this equation if you want to build a wind turbine or if you want to calculate the power needed for a vehicle of any type to overcome drag to name just a few examples for the use of this equation.
 
  • #14
electrodacus said:
It gives me an error as video unavailable.
It's the theme music from the movie Jaws. It's meant to signify that you probably should not have tried to go for a swim at the same beach where you were bitten twice before...
 
  • #15
berkeman said:
It's the theme music from the movie Jaws. It's meant to signify that you probably should not have tried to go for a swim at the same beach where you were bitten twice before...
:) funny.
But I do not think it applies to this case. I do not see how I was bitten ? To me it looks more like I was banned because people were thinking I invented or misused equations.
There is also a calculator that properly applies this equation correctly https://www.electromotive.eu/?page_id=12&lang=en
 
  • #16
electrodacus said:
To me it looks more like I was banned because people were thinking I invented or misused equations.
Thread closed again temporarily for Moderation. I will try to find your quote in your previous threads where you acknowledged that the video demonstrations were real. Give me a day or so please...
 
  • #17
For if @berkeman chooses to re-open the thread:
electrodacus said:
This is strictly about this equation.
Then since the question about the equation has been answered, the thread is finished, right?

[Edit] @berkeman has decided to keep the thread closed.
 
Last edited:
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