Drag Force: Mass & Why It Doesn't Affect Object

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Drag force is primarily influenced by the shape, cross-sectional area, and the density of the air around an object, rather than the object's mass. The drag equation highlights these factors, indicating that the drag force results from the interaction between the object's surface and the airflow. Although some participants suggested that mass might affect drag due to momentum considerations, the consensus is that it does not play a role in drag force calculations. Additionally, various physical factors such as viscosity and flow state can impact drag, but these are independent of the object's mass. Ultimately, the mass of the object does not influence the drag force acting on it.
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Why drag force doesn't Depend on the mass of the Object?
 
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Well, what does drag force depend on?
 
if the drag force is the reaction force on the elastic collision between air molecules and the object , so it have to depend on the momentum of the air molecules and object momentum, is that right?
 
Drag force (and all aerodynamic forces) are the forces caused by the air flowing around an object. Only the shape of the object matters. It doesn't matter if the object is hollow or filled with lead.
 
okay ,but if you see it as a collision and the air molecule mass is constant and its initial velocity is also constant, and the object velocity is also constant but its mass is changing so the reaction force will change , so drag force must depend mass.
 
The drag equation suggests it's the object's density, cross-sectional area, and shape that affects the force acting on it by the air.
 
A Lazy Shisno said:
The drag equation suggests it's the object's density, cross-sectional area, and shape that affects the force acting on it by the air.
That's the air density, not the object's density.
 
FactChecker said:
That's the air density, not the object's density.
Sorry, yes, you're right. I'm not sure how I forgot that.
 
A Lazy Shisno said:
The drag equation suggests it's the object's density, cross-sectional area, and shape that affects the force acting on it by the air.

The "drag equation" also is not based upon first principles and does not capture all of the relevant physics contributing to drag. It's just an empirical relationship between the drag force, area, and the dynamic pressure (##\rho V^2/2##). The drag coefficient relates those quantities across a wide range of conditions, but tells you nothing about what actually contributes to the drag. Viscosity, ratio of specific heats, and Mach number can also all play a role, for example. So can the laminar-turbulent state of the boundary layer, the surface quality, and in extremely high-speed flows, chemical reactions.

The important thing is that in none of those cases does the mass (or density) of the object play a role.
 
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