Abslyut nol harorat

The average power is the physical quantity determined by the ratio of the work of the force or system of forces during a finite period of time to this time interval:
A power (instantaneous power) is a physical quantity equal to the limit to which the average power tends with an infinite decrease in the time interval:
Hydroaeromechanics is a branch of physics in which the laws of equilibrium and motion of liquids and gases are studied, as well as the interaction of liquids and gases with solids. In hydroaerostatics, the conditions and regularities of the equilibrium of liquids and gases under the action of the forces applied to them are considered and, in addition, the equilibrium conditions for solids in liquids or in gases.
Hydroaerodynamics studies the laws of motion of liquids and gases, as well as the interaction of liquids and gases with solids in their relative motion.
An incompressible fluid is a droplet liquid or a gas whose density dependence on the pressure in a given problem can be neglected. If the dependence of the gas density on pressure can not be neglected, then such a gas is called a compressible fluid.
Archimedes' Law: a body that is immersed in a liquid is acted upon by a buoyant (Archimedian) force equal in magnitude to the force of gravity of the fluid displaced by the body.
The motion (flow) of a fluid is called stationary (steady) if at certain points in space the velocity of the fluid does not depend on time.
If at fixed points of space the velocity of a fluid changes with time, the motion is called nonstationary (unsteady).
Laminar flow is the flow of a liquid, in which its adjoining layers move without mixing. When the liquid layers are stirred, the flow is called turbulent.
Internal friction (viscosity) is the phenomenon of the appearance of forces that prevent relative movement of layers of liquid or gas.
An ideal (inviscid) liquid is a continuous medium in which the viscosity is absent or it can be neglected.