The buoyant force of air? Concept question

In summary, when weighing an object that is immersed in water, we need to correct for the buoyant force of the water. This is because air is also considered a fluid and has a set atmospheric pressure. However, since the density of air is much lower than that of water, the buoyancy correction for weighing objects in air is usually small and only applied when high accuracy is needed. If the object has a similar density to air, such as an inflated balloon, the buoyancy correction is more significant and must be taken into account.
  • #1
laddoo12
3
0
if we weigh a metal object which is immersed in water, we have to correct the buoyant force for water. Air is a fluid. Why don't we correct for the buoyant force of the air when we weigh it in the air?

What i think it may be is because we have a set atmospheric pressure being 1.013 Kpa in the air and we measure everything in relation to the world relative to that?

Can someone discuss why this is, I'm not sure what i said onto is a logical quick explanation, but there should be much more to this?
 
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  • #2
The density of air at sea level is about 1/800 the density of water, and the buoyancy correction for weighing most objects in air is small (less than 0.1%). The correction is applied when weighing objects very accurately.

Of course if the object being weighed has a density of the same order of magnitude as air (e.g. an inflated balloon) the correction is not negligible!
 
  • #3
..especially a balloon inflated with helium.
 

1. What is the buoyant force of air?

The buoyant force of air is the upward force exerted by air on an object that is immersed in it. It is a type of fluid force that acts in the opposite direction of gravity and is responsible for making objects float.

2. How is the buoyant force of air calculated?

The buoyant force of air is calculated using the formula Fb = ρair * V * g, where ρair is the density of air, V is the volume of the object, and g is the acceleration due to gravity. This formula is based on Archimedes' principle which states that the buoyant force is equal to the weight of the displaced fluid.

3. What factors affect the buoyant force of air?

The buoyant force of air is affected by the density of the object, the density of air, and the volume of the object. The greater the density of the object, the greater the buoyant force required to make it float. Similarly, the denser the air, the greater the buoyant force. The volume of the object also plays a role as a larger volume displaces more air, resulting in a greater buoyant force.

4. What is the difference between the buoyant force of air and the buoyant force of water?

The buoyant force of air and the buoyant force of water are both fluid forces that act in opposite directions of gravity. However, the main difference is that air has a lower density than water, so it exerts a smaller buoyant force on objects. This is why objects that float in water may not float in air.

5. How does the buoyant force of air affect the flight of an airplane?

The buoyant force of air plays a crucial role in the flight of an airplane. As the airplane moves through the air, its wings are designed to create a pressure difference that results in lift, which is the force that counters the weight of the airplane. The buoyant force of air also helps to keep the airplane in the air by pushing upwards on its wings and body, making it easier to control and maneuver.

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