Understanding the Relationship Between Drag Force and Velocity in Physics

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Discussion Overview

The discussion centers on the relationship between drag force and velocity in physics, specifically examining the proportionality of drag force to velocity and the implications of the units of the constant involved in the drag force equation.

Discussion Character

  • Debate/contested

Main Points Raised

  • Some participants propose that the drag force can be modeled as F_d = -kv, where k is a constant.
  • One participant questions the appropriateness of the units of k, stating they are "strange" as they are kg/s.
  • Another participant challenges the notion of strangeness, arguing that the units make sense as they relate force, mass, and velocity.
  • A further comment raises a hypothetical about quoting force values in terms of kg.m.s-2, suggesting a comparison to clarify the discussion on units.

Areas of Agreement / Disagreement

Participants express differing views on the appropriateness of the units of the constant k in the drag force equation, indicating a lack of consensus on whether the model is flawed based on these units.

Contextual Notes

The discussion does not resolve the implications of the units of k or the validity of the drag force model, leaving these points open for further exploration.

finchie_88
If the force of drag is proportional to the velocity, then:
[tex]F_d = -kv[/tex]
However, the units of k are very strange. Does this mean that the model is completely wrong?
 
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finchie_88 said:
If the force of drag is proportional to the velocity, then:
[tex]F_d = -kv[/tex]
However, the units of k are very strange. Does this mean that the model is completely wrong?

What do you mean by "strange"? What did you expect the units of "k" supposed to be?

Note that just because something is a constant, doesn't mean it doesn't have any units, or that it must have only certain types of units.

Zz.
 
By strange, I mean kg/s. Which seems strange in the idea of projectiles or falling objects (in rocket motion it would make much more sense).
 
I still don't see why it is strange. Why does having the unit of kg/s for the constant seem strange? It is, after all, connecting a "force" (which has a mass dependence), to a velocity (which has a time rate of change dependence).

Sounds perfectly un-strange to me.

Zz.
 
Would you consider it strange if we quoted the value of a force as 5 kg.m.s-2?
 

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