# Weight in Vacuum vs Atmosphere: A Question

• northern expo
In summary, the weight of an object in a vacuum is the same as the weight in an atmosphere, but the buoyant force of air has a small effect on the downward force.
northern expo
not sure if this question has been asked before, but is the weight of an object the same in a vacuum compared to weight in an atmosphere. the concerns of this question is that do we need to consider that our atmosphere provides some boyancy on our mass to change the value of weight.

If by "weight" you mean the downward force that a stationary object exerts on whatever is supporting it against gravity, yes, it depends on the buoyant force of the surrounding medium. If the medium is air, we usually ignore this effect, especially in introductory textbook examples, but if you need a lot of precision you may have to take it into account. Or if the medium is dense, e.g. water.

Weight is the force an object feels due to gravity.
So you only feel it if you are standing on (or near) an object

Yes the boyancy of air has a small effect on the downward force.
I suppose you could split hairs and say this doesn't change the weight, it only changes the total downward force but in everyday language this is the weight - you could always say "apparent weight" if you want to be more precise

what is the bouyant force of air??

northern expo said:
what is the bouyant force of air??

If a person has a mass of 75kg and the density of water, they will have a volume of 0.075m^3 so the bouyancy of air only makes about 100g difference.

It gets more complicated when you want to weight something - for really precise work you should take into account density difference between object and weights material.

northern expo said:
what is the bouyant force of air??

Buoyancy is the force exterted upward to keep a given object afloat. In the case of air, buoyancy is proportional to altitude. As an object rises in the air its buoyancy decreases as the density of the surrounding air decreases and vice-versa as the object falls.

Hope I was able to explain that well.

## 1. What is the difference between weight in vacuum and weight in atmosphere?

The weight of an object in vacuum is the force exerted on that object by gravity in the absence of any air or other medium. In contrast, the weight of an object in atmosphere is the force exerted on that object by gravity in the presence of air or other medium. This means that the weight in vacuum will be less than the weight in atmosphere due to the buoyancy of the air.

## 2. Why is weight in vacuum important in scientific experiments?

Weight in vacuum is important in scientific experiments because it allows researchers to accurately measure the mass of an object without the interference of air resistance or buoyancy. This is especially important in experiments involving gases or fluids, as the weight in atmosphere may not accurately reflect the true mass of the object being studied.

## 3. Does the weight in vacuum of an object change depending on its shape?

Yes, the weight in vacuum of an object can change depending on its shape. This is because the shape of an object can affect its buoyancy in air, which in turn affects its weight in atmosphere. However, in a vacuum, where there is no air to provide buoyancy, the weight of an object will be solely determined by its mass.

## 4. How is weight in vacuum measured?

Weight in vacuum is typically measured using a device called a vacuum balance. This device consists of a balance beam with two pans, one of which contains the object being weighed, and the other containing calibrated weights. The balance beam is placed in a vacuum chamber, and the weights are adjusted until the balance is level, indicating that the weight of the object in vacuum is equal to the weight of the calibrated weights.

## 5. Can weight in vacuum ever be greater than weight in atmosphere?

No, weight in vacuum can never be greater than weight in atmosphere. This is because the presence of air or other medium in the atmosphere will always exert a buoyant force on an object, making its weight in atmosphere greater than its weight in vacuum. However, in a perfect vacuum, where there is no air or other medium, the weight in vacuum and weight in atmosphere would be equal.

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