Force on a body through air pressure

In summary, the conversation discusses the possibility of using air pressure to lift a big block of steel, with the use of a sealed container and a movable piston. It is mentioned that air pressure acts on all sides but would only have a real effect on the movable surface. The concept of a piston is also explained, with an airplane being given as an example. The conversation ends with a mention of the strength of air pressure on Earth.
  • #1
Nythe
4
0
If a body,let's say a big block of steel, has a net downward force of weight of 1000N, would it be possible to lift the block using air pressure? I mean, if you put air in a completely sealed container with a movable piston on top and you pressurized such air to an appropriate pressure, then by formula: pressure=force/area, wouldn't it be possible to achieve a force equal to or more than the weight of the body? And if this could be done and the entire container is attached to the underside of the body, would the body not constantly levitate a little because of the net upward force?
 
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  • #2
Welcome to PF.

Air pressure acts on the top and the bottom of the deviece, so it cancells out. The only way to get air pressure to move something is to use a vacuum pump to remove air from one side.
 
  • #3
Yes, its true that air pressure acts in all directions but if, in this container, let's say a cuboid for hypothetical purposes, 5 of the 6 sides are completely sealed and one side is a movable surface, the force would act on all sides but would only have a real effect on the movable surface. I don't think gas pressure will transmit through a solid, immovable surface.
 
  • #4
Nythe said:
If a body,let's say a big block of steel, has a net downward force of weight of 1000N, would it be possible to lift the block using air pressure? I mean, if you put air in a completely sealed container with a movable piston on top and you pressurized such air to an appropriate pressure, then by formula: pressure=force/area, wouldn't it be possible to achieve a force equal to or more than the weight of the body? And if this could be done and the entire container is attached to the underside of the body, would the body not constantly levitate a little because of the net upward force?
Could you pressurize air within some container to lift a piston plus the added weight resting on it? Sure, why not.
 
  • #5
Nythe said:
Yes, its true that air pressure acts in all directions but if, in this container, let's say a cuboid for hypothetical purposes, 5 of the 6 sides are completely sealed and one side is a movable surface, the force would act on all sides but would only have a real effect on the movable surface.
This arrangement is generally called a "piston". Although typically they are made cylindrical rather than cubic.

Nevermind, I see Doc Al already mentioned that.
 
  • #6
Nythe said:
If a body,let's say a big block of steel, has a net downward force of weight of 1000N, would it be possible to lift the block using air pressure?

Yeah, isn't that how airplanes work?
 
  • #7
Lsos said:
Yeah, isn't that how airplanes work?

Good example, the velocity at the top of the wings is faster so the pressure is more under the wings. And an airplane is heavy.

Air pressure is so strong on Earth that if you depressurized your house your lungs would burst and your blood would boil. and then your house would implode.
 
  • #8
A better example would be a pneumatic lift.
 

1. What is air pressure?

Air pressure is the force exerted by the weight of air molecules on a surface. It is caused by the collisions of air molecules with the surface and is measured in units of pressure, such as pounds per square inch (psi) or pascals (Pa).

2. How does air pressure affect objects?

Air pressure can affect objects in various ways, depending on the surface area and shape of the object. When air pressure is higher on one side of an object, it can create a net force on the object, causing it to move or deform. For example, a balloon inflates due to the higher air pressure inside than outside.

3. What is the relationship between air pressure and altitude?

The higher the altitude, the lower the air pressure. This is because air molecules are more spread out at higher altitudes, resulting in lower air pressure. This is why it can be more difficult to breathe at high altitudes, as there is less air pressure pushing oxygen into our lungs.

4. How does air resistance affect the force on an object?

Air resistance is a force that opposes the motion of an object through air. This can reduce the net force on an object, resulting in a lower acceleration. For example, a parachute creates air resistance that slows down the descent of a skydiver.

5. How can we calculate the force on a body through air pressure?

The force on a body through air pressure can be calculated using the formula F = PA, where F is the force, P is the air pressure, and A is the surface area of the object. Additionally, Bernoulli's principle can be used to calculate the force on an object in a moving fluid, such as air.

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