# Is air resistance affected by both mass and surface area?

If so, which has the biggest impact?

• Sep 11, 2014 at 21:45

What a layman calls "air resistance", a physicist would call drag. Drag is affected by the area and shape of the solid object, the speed and orientation of the object relative to the fluid, and various properties of the fluid such as its density and kinematic viscosity. The drag on a solid, rigid object isn't affected by the object's mass.

However, drag is just the portion of the force on the object that's due to the fluid. The net force on the object will of course be affected by the object's mass, assuming that gravity is one of the forces on the object.

• So air resistance is not a real force and is more like a collective term for the different forces that slow down an object (or act against the motive force/thrust) while traveling through air? Sep 11, 2014 at 19:51
• @user58953 It is a real force, much in the same way that friction (e.g., rubbing your shoe on a carpet) is a real force. Many parameters go into determining the drag, but it is a single real force. What RedAct is trying to say, beyond your question, is that drag is not the only force on an object as it travels through a liquid. If there's gravity, gravity can slow down or accelerate the object depending on direction. But that has nothing to do with drag. Sep 11, 2014 at 21:06
• Air resistance (drag) most certainly is a real force, or rather a collection of forces, all of which are attributable in one way or another to a body moving through a fluid, and all of which oppose this movement. Sep 11, 2014 at 21:08
• I'm not sure what you mean by "not a real force" or "different forces". Drag is the force acting opposite to the motion of the object relative to the surrounding fluid, that's due to the surrounding fluid. You can take the total drag to be the sum (integral, really) of the drag on each of a bunch of little pieces of the object's surface, if that's what you mean. But all of the various attributes of the object and the fluid that affect how much the drag is (area, speed, density, viscosity, etc.) are not forces, if that's how you meant that sentence. Sep 11, 2014 at 21:08
• Just to clarify my earlier comment: the drag on a little part of a whole object's surface is different from what the drag would be on that piece of the object alone if it were removed from the object. I didn't mean to imply that drag is additive in that way. Sep 11, 2014 at 21:17