P10 - Pressure in liquids and gasses Flashcards
Paper 2
What is a fluid?
A substance that can flow
At what angle do particles exert a force when they collide with a surface?
Right angles to the surface
What is pressure?
The force acting per square metre on a surface
What is pressure measured in?
Pascal (Pa), which is equal to one newton per square metre
How do you calculate the pressure caused by a column of liquid?
Height of column (m) x density of the liquid (kg/m3) x gravitational field strength
P = hpg
What is the atmosphere?
A thin (relative to the size of earth) layer of air (60 miles)
What is atmospheric pressure caused by?
Air molecules colliding with surfaces
When will an object sink in a fluid?
When its weight is greater than its upthrust
When will an object float?
When its weight is equal to its upthrust
What is upthrust?
The resultant force due to the difference in pressure between the top and bottom surfaces of an object submerged in a fluid
What happens to the atmospheric pressure as you gain altitude and why does it happen?
The density of the air decreases, fewer air molecules as you go higher - there is less weight of the air above the surface and fewer air molecules so density of the atmosphere decreases
