Understanding the Relationship Between Drag Force and Velocity 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?

 

[ZapperZ]

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.

 

[finchie_88]

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).

 

[ZapperZ]

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.

 

[Hootenanny]

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