Podnośnik hydrauliczny
Hydraulic systems operate according to Pascal’s law
http://home.planet.nl/~brink494/frm_e.htm
Pascal's law — developed by French mathematician Blaise Pascal — states that when there is an
increase in pressure at any point in a confined fluid, there is an equal increase at every other point in
the container.
Definition of pressure:
If F is the magnitude of the normal force on the piston and A is the surface area of a piston, then the
pressure, P, of the fluid at the level to which the device has been submerged as the ratio of the force
to area.
Since the pressure is force per unit area, it has units of N/m 2 in the SI system.
Another name for the SI unit of pressure is Pascal (Pa)
An important application of Pascal's law is the hydraulic press. A force F 1 is applied to a small piston
of area A1. The pressure is transmitted through a liquid to a larger piston of area A 2. Since the
pressure is the same on both sides, we see that P = F1/A1 = F2/A2. Therefore, the force F2 is larger
than F1 by multiplying factor A2/A1. Hydraulic brakes, car lifts, hydraulic jacks, and forklifts all make
use of this principle.
Siła wyporu
http://web.mit.edu/pmavrom/Public/ariana/buoyancy/student1.html - Let's
learn
about BUOYANCY
http://www.getsmarter.org/mstv/L3_a.cfm - How can a hundred-thousand-ton aircraft
carrier possibly float on water?
Archimede's Principle:
The buoyant force is equal to the weight
of the liquid displaced.
Fluid Mechanics – mechanika płynów (The best !!!)
Joseph F. Alward, PhD
Department of Physics
University of the Pacific
Woda – ciecz niezwykła
(…) chemists have been disagreeing for the past 40 years over how water molecules arrange
themselves in a liquid drop. (…)
http://www.lbl.gov/Science-Articles/Archive/sabl/2005/October/03-water-contoversy.html
The Microscopic Picture of Gas Behavior: Kinetic Theory of Gases
http://www.chemistry.wustl.edu/~edudev/LabTutorials/Airbags/airbags.html
In a microscopic view, the pressure exerted on the walls of the container is the result of
molecules colliding with the walls, and hence exerting force on the walls (Figure 3). When
many molecules hit the wall, a large force is distributed over the surface of the wall. This
aggregate force, divided by the surface area, gives the pressure.
The molecules are constantly moving in random directions. When a molecule hits the
container wall (green), it exerts a tiny force on the wall. The sum of these tiny forces, divided
by the interior surface area of the container, is the pressure.
The kinetic-molecular theory (the theory of moving molecules) is summarized by the
following statements:
1. Gases consist of large numbers of molecules that are in continuous, random motion. (The
word molecule is used here to designate the smallest particle of any gas; some gases, such as
the noble gases, consist of individual atoms.)
2. The volume of all the molecules of the gas is negligible compared to the total volume in
which the gas is contained.
3. Attractive and repulsive forces between gas molecules are negligible.
4. Energy can be transferred between molecules during collisions, but the average kinetic
energy of the molecules does not change with time, as long as the temperature of the gas
remains constant. In other words, the collisions are perfectly elastic.
5. The average kinetic energy of the molecules is proportional to the absolute temperature. At
any given temperature the molecules of all gases have the same average kinetic energy.
The kinetic-molecular theory gives us an understanding of both pressure and temperature at a
molecular level. The pressure of a gas is caused by collisions of the molecules with the walls
of the container, as shown in Figure 10.14. The magnitude of the pressure is determined both
by how often and how "hard" the molecules strike the walls.