Understanding the Relationship Between Drag Force and Velocity in Physics

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The discussion centers on the relationship between drag force and velocity, specifically the equation F_d = -kv, where k has units of kg/s. Participants debate whether these units are unusual, with one arguing that kg/s seems odd for projectile motion, while another counters that the units are appropriate as they relate force to velocity. The conversation emphasizes that constants can have units and that the relationship between mass and time in the context of drag force is logical. Ultimately, the appropriateness of the units is affirmed, suggesting that the model is not fundamentally flawed. Understanding these units is crucial for accurately applying the drag force concept in physics.
finchie_88
If the force of drag is proportional to the velocity, then:
F_d = -kv
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:
F_d = -kv
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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