P10 Pressure Flashcards
fluid
liquid OR gas
pressure (+ unit)
force acting per square metre of a surface - unit is pascal (Pa)
force/area
calculating pressure in a column of water
pressure = height of column (m) x density of liquid (kg/m^3) x gravitational field strength (N/kg)
p = hpg
pressure in a liquid vs depth (and how to shoe this)
as depth increases pressure increases
(pressure in a liquid is due to weight of liquid above that point)
put three holes in a water column, water from a hole in the bottom will spurt out further (more pressure)
does shape affect pressure (and how to prove this)
no
pascals vases:
The pressure at the bottom of the fluid depends upon the depth of the fluid and not on the shape of the container. The apparatus consists of a group of glass flasks of assorted shape (see figure 1) linked at their base by a communal reservoir. With the pressure being dependent on the depth of liquid only, an equilibrium situation must have the surface level in each vase equal.
upthrust
objects that are partially or completely submerged in water have experience a greater pressure on their bottom surface than on their top surface.
the difference in pressure creates an upwards resultant force - upthrust
how to tell if an object will float or sink
upthrust = weight of water displaced
an object sinks if:
weight > upthrust
mass of object in area X > mass of water in the same area
density of object > density of water
if an object is less dense than water it will float in water
atmosphere
relatively thin layer of air surrounding earth
atmospheric pressure
caused by air molecules colliding with surfaces
decreases as altitude (height above surfaces increases:
- fewer air molecules above the surface as height increases - weight of air above the surface decreases
- density of atmosphere decreases with altitude
