Pressure and Gas Flow
The unit N/m2 has the special name ‘pascal’ after the French mathematician. It is in more common use on the continent and has the symbol ‘Pa’.
Pressure Exerted by a Solid
A solid object has the ability to exert a pressure on the floor on which it stands, but this is only in a downward direction. Fluid pressure acts in all directions at the same time. The pressure exerted by a solid object is the weight of the object
divided by the area of its base. Take as an example the object shown in Fig. 6.1. If the dimensions 25, 50 and 75 are in millimetres and the weight of
the block is 5 kg, then in the different positions the pressures exerted by the base are:
It follows that, for the same weight of object, the smaller the base area, the higher the pressure that it will exert. For example, a woman wearing stiletto heels will probably make holes in wood or vinyl flooring. The same woman in shoes with large, flat heels will not damage the floors.