Pressure and pressure Differences Flashcards
what is a fluid
a liquid or gas
Describe how the particles in a fluid create pressure.
In any fluid, at what angle do the forces due to pressure act on a given surface?
at right angles to the surface
what is the equation for pressure
pressure(pa) = force(N) / area^2( metres squared)
how do you calculate the pressure of a column of liquid?
p=hpg
pressure(pa) = height(m) x density(kg/m^3)x gravitational field strength(N/kg)
Why does the pressure of a liquid increase with depth (height of the column)
because as the depth increases, there’s a greater weight of liquid acting downwards
what is the atmosphere
a thin layer of air around the earth
at high altitudes there’s less air above a surface than at lower altitudes, so what
there’s smaller weight of air acting on the surface
what happens to the density of the atmosphere with increasing altitude?
atmosphere becomes less dense
why does pressure in fluids increase with density?
as density increase, number of particles in a volume increases. weight of the fluid is greater
why are objects in a fluid subject to an upthrust?
when an object is submerged in a liquid, there’s a greater height above the bottom of the surface. The bottom of the surface experiences a greater pressure than the top and creates a resultant force upwards.
what is upthrust
the force exerted by a liquid on a submerged object
what is the size of the upthrust equal to
the weight of liquid displaced
how does an object sink and float
-floats - when its weight is equal to the upthrust
1. less dense than liquid
2.displaces a volume greater than its own weight- will rise
-sinks- its weight is greater than the upthrust
1.objects denser than liquid cant displace liquid to equal its own weight -sinks
the density of the object indicates if it will float or sink
explain why an object with a density greater than the water will always sink
upthrust = weight of displaced fluid. If density is high there’s not enough volume to displaced to produce upthrust larger than the objects weight
