# Fire Protection

Even if is not the primary extinguishing agent, it may be found combined with other agents such as foam or may be used extensively for cooling containers in liquid petroleum gas (LPG) fires. It is essential that every fire fighter understand the behaviour of water in difference circumstances.
Most of the motions that we find on earth involve friction. Friction is a force which occurs when two surfaces rub against one another. If you roll a ball slowly across the floor, the ball’s speed decreases and eventually it stops. It stops because the friction between the ball and the floor pushes against the ball and reduces its motion. When you rub your hands together, you feel the resistance due to friction. By rubbing your hands together, you are doing work. The result of this work is the heat produced.
Water when pure is colourless, odourless, and liquid with a molecular composition to two atoms of hydrogen combined with one atom of oxygen. A liter of water has a mass of 1 kilogram (1 kg), corresponding to a downward force of 9.81 newtons (N). A cubic meter of water exerts a downward force of 9810 N, or 9.81 kilonewtons (kN). This is more commonly reckoned as 10 kN. The mass of water varies with the degree of purity. Ordinary sea water ‘weighs’ approximately 10.0 newtons per liter (N/litres).
Pure water has a freezing point of 0…
It is virtually incompressible, and an increase of 1 bar only causes a decrease in volume of 0.000 002 per cent.
As a fluid, water has volume but is incapable of resisting change of shape, i.e. when poured into a container it will adjust itself irrespective of the shaper of the latter, and will come to rest with a level surface. This is because there is very little friction or cohesion between the individual molecules of which water is composed.
2. PrincipalCharacteristicsofPressure
There are six basic rules governing the principal characteristics of pressure in liquids. These are:
a. Pressure is perpendicular to any surface on which it acts
If a vessel having flat sides contains water, and that water has attained a position of rest, then the pressure on all sides of the vessel due to the weight is perpendicular to those sides, as shown by the direction of the arrows.
b. Pressure at any point of a fluid at rest is of the same intensity in all directions
In a line of piping or hose, two pressure gauges are inserted. If the water is at rest because a valve or hand-controlled branch has been shut down, the pressure gauges will register identical readings showing that the pressure at any point of a fluid at rest is the same in all directions.
c. Pressure applied from outside to a fluid contained in a vessel is transmitted in al directions
A hollow sphere with pressure gauges around the circumference has been filled with water, and pressure is applied. All the gauges will show the same pressure reading, providing that when pressure is applied to a fluid in a confined space, that pressure is transmitted equally in all directions.
d. Downward pressure of a fluid in an open vessel is proportional to its depth
If there are three