What are the differences between regimes I and II in drag forces?

In summary, the conversation discusses the concept of regimes I and II in relation to drag forces in physics. The distinction between laminar and turbulent flow regimes, as well as subsonic and supersonic flow regimes, is mentioned. The conversation also includes a request for links to websites containing more information on these topics.
  • #1
wrongusername
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So I was looking at MIT iTunes U physics videos, and the professor talked about regimes I and II in the video about drag forces. I think regime I has to do with the temperature of the medium and regime II has to do with the density. But, I cannot find that information in my 1st semester physics textbook. Nor can I find such info using Google (perhaps I'm using the wrong search terms?:rolleyes:). Can anybody provide me with links to websites containing such stuff in them?
Thank you very much! :D
 
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  • #2
I've never heard of this terminology before. It sounds very odd... I'd need to see the context of how they are using these words.
 
  • #3
There is the laminar flow regime vs. the turbulent regime. There is also the subsonic flow regime vs. supersonic. You should be able to tell which two are being distinguished from the context.
 
  • #4
Phrak said:
There is the laminar flow regime vs. the turbulent regime. There is also the subsonic flow regime vs. supersonic. You should be able to tell which two are being distinguished from the context.

Ok, thanks for the info! :smile:
 
  • #5
Both regimes are discussed here:
http://en.wikipedia.org/wiki/Drag_(physics [Broken])
Low Reynolds number drag is also called Stokes law. High Reynolds number drag (Re > 1000) corresponds to a force that is proportional to square of velocity, like an automobile at highway speeds.
 
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  • #6

1. What is the definition of drag force?

The drag force is a force that acts in the opposite direction of an object's motion through a fluid (such as air or water), and is caused by the interaction between the object and the fluid.

2. What is the difference between Regime I and Regime II drag forces?

In Regime I, the drag force is directly proportional to the object's velocity and is characterized by laminar flow. In Regime II, the drag force is proportional to the square of the object's velocity and is characterized by turbulent flow.

3. How does the shape of an object affect drag force?

The shape of an object can greatly affect the drag force it experiences. Objects with streamlined shapes (such as airplanes) experience less drag force compared to objects with non-streamlined shapes (such as cubes) because they create less turbulence in the fluid flow.

4. What factors can affect the transition from Regime I to Regime II?

The transition from Regime I to Regime II can be affected by several factors, including the object's shape, size, and speed, as well as the fluid's viscosity and density. Changes in any of these factors can cause a transition from laminar flow to turbulent flow and vice versa.

5. How is drag force calculated in Regime I/II?

In Regime I, the drag force can be calculated using the equation F = 6πμrv, where μ is the fluid's viscosity, r is the object's radius, and v is the object's velocity. In Regime II, the drag force can be calculated using the equation F = 0.5ρAv^2, where ρ is the fluid's density, A is the object's cross-sectional area, and v is the object's velocity.

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