Does the air exert a buoyant force on all objects in air or only on objects such as balloons that are very light for their size? Does the air exert a buoyant force on all objects in air or only on objects such as balloons that are very light for their size? Air exerts a buoyant force on all objects. Air has too low a density to exert a buoyant force. Air exerts a buoyant force only on objects less dense than air. Air exerts a buoyant force only on objects more dense than air.

See explanation

Explanation:

Solution:-

Buoyancy is the force that causes objects to float. It is the force exerted on an object that is partly or wholly immersed in a fluid. Buoyancy is caused by the differences in pressure acting on opposite sides of an object immersed in a static fluid. It is also known as the buoyant force. Buoyancy is the phenomena due to Buoyant Force.

It is as an upward force exerted by a fluid that opposes the weight of an object immersed in a fluid. As we know, the pressure in a fluid column increases with depth. Thus, the pressure at the bottom of an object submerged in the fluid is greater than that at the top. The difference in this pressure results in a net upward force on the object which we define as buoyancy.

- The formula for buoyant force (Fb) is given:

                           Fb = ρ*g*V

- The force acts on all objects. However, it depends on the fluid density and amount of volume displaced.

- The Buoyant force exerted by air with density = 1.225 kg/m^3 on an object with volume (V) is:

                          Fb = ρ*g*V = 1.225*9.81*V = 12.02*V

- For the similar object with mass (m), the downward weight would be:

                           W = m*g

- For the object to float the buoyant force (Fb) must be greater than weight of the object:

                          Fb > W

                          12.02*V > m*9.81

                          V / m > 0.816

- The ratio of V / m must be at-least = 0.816.

- Assuming the object is fully immersed in air, then the volume displaced V = ρ_material*V

                         ρ_material < 1 / 0.816

                        ρ_material < 1.225 or ( ρ_air )

- So the for an object to float in air its material density must always be less than that of air. That why in balloons lighter gas is used which have density less than that of air like Helium.          

not too sure thinking all accelerations are pointed down