Fluid Pressure Flashcards
what is pressure
force per unit area
what is a fluid and what does it do to a object
A fluid is either a liquid or a gas
When an object is immersed in a fluid, the fluid exerts a pressure upon the object
This pressure is in addition to the pressure already exerted by the atmosphere
what does pressure arise due to
The water pressure
Atmospheric pressure
what is the force exerted on a object by a fluid and describe it
squeezing the object
This pressure is exerted evenly across the whole surface of the fluid and in all directions
The pressure exerted on objects in fluids creates forces against surfaces
These forces act at 90 degrees (at right angles or ‘normal’) to the surface
what does air molecules colliding with a surface mean
This is due to air molecules colliding with a surface creating atmospheric pressure
These molecules create a force per area of the surface which creates the pressure
what happens when height increases
The number of air molecules (and so the weight of air) above a surface decreases as the height of the surface above ground level increases
This is also known as the density of the air
what happens to atmosphere pressure as height increases
there is always less air above a surface than there is at a lower height and the atmospheric pressure decreases with an increase in height
what happens when altitude increases
atmosphere becomes less dense so fewer air molecules able to collide with surface
fewer air molecules so less weight of molecules which contribute to atmospheric atmosphere
explain the pressure when it comes to tractor tyres
ractors have large tyres
This spreads the weight (force) of the tractor over a large area
This reduces the pressure which prevents the heavy tractor from sinking into the mud
explain pressure with a nails
Nails have sharp pointed ends with a very small area
This concentrates the force, creating a large pressure over a small area
This allows the nail to be hammered into a wall
how does pressure depend on density
A more dense liquid has a greater weight and therefore will exert a higher pressure
so a denser fluid has more particles in a given space so more particles able to collide with surface therefore higher pressure than less denser fluid
how does pressure depend on depth
as depth of fluid increases the particles above the point increases so weight increases to the pressure at the point so fluid pressure increases
