Do objects in the air have normal force?

Question

Hi! I have my physics final tomorrow and have a quick question:

Do object in the air have normal force?
I know this is basic physics and I should know this but I really do not understand Normal force.
Could someone please explain it to me ASAP?

Thanks!

Answer 1

Normal force is basically the force a plane pushes back on an object. The plane is usually solid too. If you have a block on a table, the table pushes back on the block because the weight of the block is pushing on the table. Air is usually not considered a solid plane, so no normal force is taken into consideration. However, displaced air produces a buoyant force which is about as close to a normal force as you can get for air.

Answer 2

Normal force comes from contact between two objects. Specifically, it's the repulsion of electrons in the two objects when they get too close together. It's what prevents two objects from being in the same place.



In mathematics, "normal" means a line perpendicular to a plane.

The normal force is in the direction perpendicular to the surfaces that are in contact. A flat surface exerts a normal force upward. A wall exerts a normal force horizontally. A 20 degree slope exerts a normal force at 110 degrees.

Answer 3

As my old physics professor used to say, forces come from the "touch" of another object. [There are a few "spooky" forces that do not require "touch," like gravity and the force of a magnetic field, but you probably wont see them for awhile (other than gravity which is a given)].



When you're looking for forces on an object, ask yourself, "what is touching the object?" For every "touch" there is a normal force. If a box is sandwiched between 2 other boxes, there are 2 things touching it, and it is experiencing 2 normal forces!



In your case, the box is in the air and there are no "touches", so no normal force!

[just dont forget gravity, the "spooky" force] ;)

Answer 4

Absolutely they do. A normal force is simply a force that is applied perpendicularly to a surface.



And so, as all objects in the air are subjected to the atmospheric pressure (e.g., about 15 psi at sea level) and as pressure is perpendicular to their surfaces, all objects have a normal force N = PA; where P is the pressure and A is the surface area.