Force and Pressure
Pressure and Surfaces
Pressure is the force normal to a surface / area of the surface
Pressure p = F/A
The unit of pressure is the pascal (Pa) which is equal to 1N/m^2
The force3 F or area A can be calculated by rearranging the pressure equation p=f/a to give f=pa or a=f/p
Pressure in a Liquid at Rest
The pressure in a liqyid increases with increasing liquid depth
A liquid flows until the pressure along the same horizontal line is constant
The greater the density of a liquid the greater the pressure in the liquid
The pressure p due to the column of height h of a liquid of density is given by the equation p = h p g
Atmospheric Pressure
Air molecdules collide with surfaces and create pressure on them
Atmospheric pressure decreases with higher altitude becaseu there is less air above a given altitude than there is at a lower altitude
The density of the atmosphere decreases with increasing altitude
The force on a flat object due to a pressure difference = the pressure difference x the are aof the flat surface
Upthrust and Flotation
The upthrust on an object in a fluid is an upward force on the object due to the fluid and is cause by the pressure within the fluid
The pressure at a point in a fluid dpends on the density of the fluid and the depth of the fluid at at point
An object sinks if its weight is greater than the upthrust on it when it is fully immersed