How to calculate the force and mechanical pressure

1. P = f / s
F = ps
when the object is flat on the table, the pressure is equal to gravity
F = g
liquid pressure formula
P = liquid density * g * H (depth)

2.

Pressure = pressure * force area (F = PS)

The international unit of pressure is "Newton", abbreviated as "cow", and the symbol "n"; Traditionally, in mechanics and most engineering disciplines, the word "pressure" is synonymous with pressure in physics

The pressure on the solid surface is usually the result of elastic deformation and belongs to contact force. The pressure on the surface of liquids and gases is usually the result of gravity and molecular motion. The direction of pressure is usually perpendicular to the contact surface of the object. If the direction of action of pressure is not perpendicular to the contact surface, it is usually e to the interaction of pressure and friction

extended data

the difference between pressure and pressure:

I. different definitions:

1. Pressure refers to the force acting vertically on the surface of an object

Pressure refers to the pressure on the unit area of the object

Second, the cause of formation is different:

1. Pressure is formed by mutual extrusion between objects

The pressure is not only related to the pressure, but also related to the stress area. The larger the pressure is, the smaller the stress area is and the greater the pressure is

3. Pressure P = pressure f / stressed area s (s is the area perpendicular to f)
buoyancy f= ρ Liquid GV discharge (V discharge refers to the volume of liquid (such as water) discharged by the object)
work w = fscos θθ Is the angle between the direction of force F and the direction of displacement s)
power P = w / T (P = FV)

4. V = q / {(D / 2) ^ 2 * 3.14 * 3600} v-wind speed (M / s); Q - air volume (m3 / h); D-pipe diameter (m) fan is the abbreviation of gas compression and gas transmission machinery in our country. Generally speaking, the fan includes: fan, blower, wind turbine. Gas compression and gas conveying machinery converts rotating mechanical energy into gas pressure energy and kinetic energy

5.

The selection of cylinder diameter is related to pressure, and the general pressure is 0.7mp. The cylinder area is s = f / P, P is pressure, which is 0.7mp

pressure is optional and not calculated. Generally 0.7mp

when the cylinder and cylinder block are cast as a whole, they are called integral cylinder; When the cylinder and cylinder block are cast separately, the single cast cylinder is called cylinder liner. The cylinder liner in direct contact with cooling water is called wet cylinder liner; The cylinder liner not in direct contact with cooling water is called dry cylinder liner

In addition to the static loads such as the pressure difference between the inside and outside of the cylinder and the weight of the parts installed in it, the cylinder also bears the reaction force of the steam flowing out of the stationary blade on the stationary part and the force of the connecting pipes on the cylinder under the cold and hot conditions, The cylinder is prone to plastic deformation, resulting in leakage

the load of the cylinder increases and decreases too fast, especially the rapid start-up, shutdown and the large temperature change when the working condition changes, the incorrect way to warm the cylinder, and the premature opening of the insulation layer ring the shutdown and maintenance, resulting in great thermal stress and thermal deformation on the cylinder and flange

the cylinder proced stress in the process of machining or after repair welding, but the cylinder was not tempered to eliminate it, resulting in large resial stress and permanent deformation in operation

6. In short, (1) pressure is a force; The pressure is the physical quantity that indicates the effect of pressure
(2) the force that presses vertically on the surface of an object is called pressure; The pressure on the unit area of an object is called pressure. So the pressure is not only related to the pressure, but also related to the area under force
(3) the unit of pressure is n; The unit of pressure is PA, and PA and N / M & # 178; It is the same.
supplementary understanding knowledge:
pressure:
(1) the definition of pressure: the force vertically pressed on the surface of an object is called pressure.
(2) the cause of pressure: e to extrusion deformation; Note: pressure is not always caused by gravity Note: pressure is contact force)
(3) the conditions of pressure: there is contact and deformation between objects
(4) the magnitude of pressure: the magnitude of pressure can only be determined by force analysis of the object. Note: only when the object is placed on a horizontal plane, it is not subject to other external forces in the vertical direction (only gravity and supporting forces) and the system is in equilibrium, the pressure of the object on the horizontal plane can be said to be equal to gravity in value, that is, f = G
(5) direction of pressure: perpendicular to the surface of the stressed object and pointing to the interior of the stressed object
(6) the acting point of pressure: on the contact surface of the stressed object
(7) physical quantity symbol of pressure: f or f pressure; International system unit of pressure (SI system): Newton (n).
pressure:
(1) definition of pressure: in physics, the pressure on the unit area of an object is called pressure, that is: pressure = pressure / area under force.
(2) pressure formula: P = f / S; Where p is pressure Pascal (PA); F - pressure - Newton (n); S-area-square meter (m ^ 2)
(3) applicable scope of the formula: applicable to solid, liquid and gas; But the pressure proced by liquid is not necessarily equal to its own gravity.
(4) the commonly used units of pressure are: HPA, kPa [1kPa = 103pa], MPA [1MPa = 106pa]
(5) the physical meaning of pressure: pressure is the physical quantity that indicates the effect of pressure, so the size of pressure is not only related to the size of pressure, but also related to the size of stressed area< (6) methods of increasing pressure:
① when the pressure f is constant, the stress area s should be reced< When the stress area s is fixed, the pressure F should be increased< (7) methods to rece the pressure:
① when the pressure f is constant, increase the stress area s< When the stress area s is fixed, the pressure f decreases
③ if conditions permit, the pressure f can be reced and the stress area s can be increased at the same time

7. P equals f / s

8. Dlnp /, P is the formula of temperature and pressure of saturated steam, where = △ vaphm, enthalpy of evaporation RT^2); DT = △ vaphm /, according to clauseus Clausius equation

9. S = f / P (stressed area = pressure) ÷ (pressure)

10.

Atmospheric pressure calculation: there are usually equilibrium condition method and Newton's law of motion method (the formula is only a rough calculation, and sometimes the measured value is not accurate, everything should be subject to the actual situation)

1. After Torricelli measured the air pressure, people calculated the mass of air per unit area through the formula P = f / s. Then apply the density of the air, calculate the volume, and divide it by the mass to know the distance from the ground to the top of the atmosphere

When the volume of gas, the amount of substance and the absolute temperature are known, the gas pressure can be calculated by the formula PV = NRT (where R is a constant, r = 8.314 PA · m3 / mol · K or r = 0.0814 atmospheric pressure · L / mol · K). There are also deformation formulas PV = MRT / m, P= ρ RT/M

3, P = P mercury GH (mercury density * 9.8 * mercury column height = standard atmospheric pressure)

the unit of air pressure is 100 Pa, taking one decimal place; Some also take the millimeter mercury column height as the unit, takes two decimal places. The conversion relationship between mm and HPA is

1 HPA = 0.750069 mm (height of mercury column) ≈ 3 / 4 mm (height of mercury column)

1 mm = 1.333224 HPA ≈ 4 / 3 HPA

the atmospheric pressure observation in China was recorded with MM mercury column height before 1953 and HPA after 1954, It must be converted to the same unit

< H2 > extended data

the most common instruments for measuring air pressure are mercury barometer and empty box barometer. It is also a relatively accurate instrument

three centuries ago, the city of madeburg, Germany, concted an experiment in public. Otto Grick, the mayor and inventor of the ventilator, combined two hollow copper hemispheres with a diameter of 37 cm to make them airtight, and then used the ventilator to extract the air from the copper ball. Four strong horses are tied to the ring of each hemisphere and pulled in the opposite direction at the same time. The two hemispheres cannot be separated

finally, 16 horses were used, and with a loud noise, the copper ball split into two. This is the famous madeburg hemispheric experiment. The experiment shows that air not only has pressure, but also has great pressure. The average surface area of an alt's body is 2 square meters, and the atmospheric pressure on his whole body is 200000 Newton

atmospheric pressure is atmospheric pressure. Air has weight, and pressure is the force that the atmosphere exerts on a unit area. The so-called pressure of a place refers to the total weight of the air column extending vertically upward to the top of the atmosphere per unit area of the place. In meteorology, it is often used as a unit of measurement of air pressure. Specifically, it is stipulated as follows: when the sea level with a temperature of 0 ℃ and a latitude of 45 ℃ is taken as the standard pressure, it is called one atmospheric pressure, and its value is 760 mm mercury column high, or equivalent to 1013.25 HPA