In pressure calculation, P = f / s, f means pressure. How to calculate pressure?

In pressure calculation, P = f / s, f means pressure. How to calculate pressure?

It depends on your conditions!
If you are the air pressure, or water pressure or something! Then directly use f = G
If you want the pressure of an object under the action of an external force, you need to know how the pressure comes from
For example, if you press an object on the wall by hand, the pressure is the pressure of the hand on the object
If there is pressure on the slope, then the resultant force should be decomposed into pressure perpendicular to the slope
Wait, wait, wait~

There is such a fact in Physics: when the pressure f is constant, there is an inverse proportional function between the pressure P and the stressed area s, which can be expressed as P = f / s
If you put it on the table, the pressure on the table is 200 Pa. if you put it upside down, what is the pressure on the table?

200 △ 2 / 3 = 300 pa
Because the pressure f is constant, that is, f = PS
Let the bottom area be unit 1, then the upper bottom area is 2 / 3
So there is 1 × 200 = 2 / 3 × P bottom surface
P bottom = 300 pa
That's the answer. You have to calculate the contact area for the pressure on the table!

[physical liquid pressure] the difference between P = f / s and P = density * h * g, under what conditions to use it, and how to calculate the internal pressure of irregular objects, and why to calculate it

P = f / S is used for tabletop, such as small wood block, while the other one is used in liquid. If it is irregular, the pressure should be calculated first, and then f should be calculated according to the pressure