# Calculating the air pressure exerted on the body

## Summary:

Air pressure body 1.9m2

## Main Question or Discussion Point

Good morning all,

How do you calculate the air pressure exerted on an average human of 1.9m2

I know the air pressure is 1.01kPa.

Do I do, F = PA? 1.01kPa x 1.9?

What are the calculations step by step? and what is it in bars?

Does that mean it is 1.919 bar?

Thank you,

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jbriggs444
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What are the calculations step by step? and what is it in bars?
Archimedes worked it out a long time ago.

Force is a vector quantity. If you add up the force from pressure on all parts of your body, most of it will cancel out. The force on your front side will cancel the force on your back. The force on your left side will cancel out the force on your front. The force on your bottom side will almost cancel the force on your top side.

The reason that the vertical force from pressure does not exactly cancel is that air pressure is just a bit higher at your feet than at your head.

What Archimedes worked out is that the net force is given by the [weight] density of a fluid multiplied by the volume of that fluid which is displaced by a body.

So find the volume of your body. Your mass in kilograms will be pretty close to your volume in liters.

Find the density of air in kilograms per liter. (Google says 0.129 grams per liter. So 0.000129 kg/l)

Multiply the two and multiply by the acceleration of gravity. (9.8 meters/sec2)

The result will be the net upward force in newtons.

Note that the 1.9 m2 surface area does not enter in to this calculation. Nor is the result properly expressed in units of pressure. If you sum a pressure over a surface you get a force.

• Chestermiller and russ_watters