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On the formula of physical pressure Why don't I use the formula P / S = P / s for the bottom of a cylinder? Why don't I use the formula P / s for the bottom of a liquid
It is correct to use p = f / s for solid and P = pGH for liquid
However, P = f / S is also applicable to the bottom pressure of the liquid in the cylindrical container (solid with the same cross section). Similarly, P = pGH is also applicable to the opposite pressure of the cylindrical solid (regular solid)
For the liquid problem, the pressure is calculated first, then the pressure; for the solid problem, the opposite is true
Calculation formula of liquid pressure (detailed)
P = liquid density * g * h
Density is the density of the liquid into which the object is immersed, not the density of the object
G gravity constant
H is the depth of the object in the liquid
What is the formula for calculating the pressure of liquid?
P=ρgh
On the calculation formula of liquid pressure
Isn't it possible to deduce P = roll * g * h from P = f / S? Why is the result of the former formula different from that of the latter when calculating the liquid pressure? Aren't the two formulas equal?
Yes, P = ρ * g * h can be derived from P = f / s, but it is derived on the premise that the liquid container is a regular and uniform cylindrical container, so the application condition of the formula P = f / S is only applicable to this kind of cylindrical container. However, the formula P = ρ * g * h can be extended to any shape container according to the characteristics of the liquid itself (fluidity, connecter principle, Pascal's law, etc.), In fact, the derivation of the formula for the internal pressure of liquid can not be derived by the formula P = f / s, but by a more general method, the integral of the potential function of the mass force, just because it is beyond the syllabus of middle school
Supplementary notes:
When the cylinder is not upright, the pressure of liquid on the bottom of the container can be calculated by P = ρ GH, but not by P = g / s;
The pressure of liquid on the bottom of container can be calculated by F = PS = ρ GHS
Because students have many questions about this problem, the two formulas P = f / s and P = ρ GH are explained as follows:
The formula of liquid pressure P = ρ GH can be derived from P = f / s, but it is derived on the premise that the liquid container is a regular and uniform cylindrical container. Therefore, the service condition of formula P = f / S is only applicable to this kind of cylindrical container (this is different from that of solids, and the pressure between solids can always be calculated by P = f / s). However, the formula of P = ρ GH is based on the characteristics of liquid itself (fluidity, The principle of connecter, Pascal's law, etc.) can be extended to any shape container, as long as the connected liquid with uniform density can be used. In fact, the derivation of the formula of the internal pressure of the liquid can not be deduced by the formula P = f / s, but by a more general and more general method - the integral of the potential function of the mass force, which is beyond the syllabus of middle school
Because of the fluidity and non tensility of the liquid, there is no tensile stress and shear stress in the static liquid, but only compressive stress (i.e. pressure). A tiny hexahedron is arbitrarily taken out from the static liquid, which is in equilibrium under the combined action of the pressure of the six sides and its own gravity, It is concluded that the pressure in all directions acting on the same point is equal, that is, the pressure is only related to the position coordinate, but has nothing to do with the azimuth, that is, P = f (x, y, z). Then imagine that the coordinate x-o-y is on the horizontal plane, and Z is the vertical downward coordinate. The pressure of liquid is caused by the mass force of liquid. When the liquid is stationary to the earth, it is caused by gravity, The components of unit mass force of liquid with mass m = 1 in each coordinate are x = 0, y = 0, z = g. the differential relationship between pressure and mass force in liquid is
DP = ρ (xdxydy + ZDZ) = ρ (0 * DX + 0 * dy + GDZ) = ρ GDZ (it can be seen from this equation that there is no pressure difference on the same horizontal plane, and the horizontal plane is an isobaric plane, that is, the left and right pressures before and after are equal, and the pressure only changes in the direction of gravity). From z = 0 of water surface to Z = h of water depth, P = ρ GH is obtained from the integral formula, As long as the same density of connected static liquid can be applied!
The calculation formula of liquid pressure is as follows______ (ρ is the density of the liquid, in units of______ H is the depth from a point in the fluid body to______ Distance.)
The calculation formula of liquid pressure is p = ρ GH, where ρ is the density of liquid, the unit in the international system of units is kg / m3, and H is the vertical distance from the point to the liquid level. So the answer is: P = ρ GH; kg / m3; liquid level
If two angles are not equal, then they are not opposite vertex angles
Original proposition: opposite vertex angles are equal [if two angles are opposite vertex angles, then the two angles are equal]
This proposition is true, and the converse proposition of this proposition is:
If two angles are not equal, then the two angles are not opposite to the vertex
Therefore, this sentence is correct
If angle 1 and angle 2 are opposite vertex angles, and 5 ∠ 1-2 ∠ 2 = 90 degrees, calculate the degree of ∠ 1 + 2
∵∠ 1 and ∠ 2 are opposite vertex angles
∵∠1=∠2
∴5∠1-2∠2=5∠1-2∠1=90°
∴∠1=30°
∴∠2=∠1=30°
∴∠1+∠2=60°
If the two sides of an angle are () on both sides of another angle, the two angles with this relationship are opposite vertex angles, opposite vertex angles ()
RT
If two sides of an angle are opposite to each other (opposite extension line), the two angles with this relationship are opposite vertex angle, opposite vertex angle (equal)
If angle 1 and angle 2 are opposite vertex angles, and angle 5 1-2, angle 2 = 90 °, find angle 1 + angle 2
60°
Definition of vertex angle
Excuse me: what is the correct concept of vertex angle?
There are two versions:
1. When two lines intersect, the two corners with only one common vertex but no common edge (or the two sides of one corner are the opposite extension lines of the two sides of the other corner) are called opposite vertex angle and two lines intersect to form two opposite vertex angles
2. They have a common vertex O and no common edge. Two angles like this are called opposite vertex angles
Excuse me, which one is right?
Our teacher said that the two sides of one corner must be the opposite extension lines of the two sides of the other corner,
Is it true that the positions of the two opposite vertex angles must be relative?
Both are true, but one is to define and the other is to give examples
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