pressure Flashcards
what is pressure
it is defined as the force acting on a unit area
what is the formula for pressure
p=f/a (pressure=force/area)
what is 1Pa equal to
Ipa is equal to a force of 1N acting on an area of 1m2 (1pa=1N/m2
what is the si unit for pressure
Pascal (Pa) or N/m2
what are the 2 factors that depend on pressure
area and force
how does force affect pressure
when force increases pressure increases, provided the area is constant and when force decreases the pressure will also decrease so the pressure is directly proportional to force
how does area affect pressure
when area increases the pressure decreases and when area decreases the pressure increases, provided the force stays constant so the pressure is indirectly proportional to the area
explain liquid pressure
the liquid in a container exerts pressure because of its weight, the gravitational force tries to pull the liquid downward in its container, this causes pressure on the container and pressure on any object into the liquid
what is the formula for liquid pressure
P= pgh P= pressure (Pa) p= rho (density of the liquid) g= gravitational field strength h= height/depth
what are the properties of liquid pressure
1- the pressure acts in all directions as the liquid pushes on every surface in contact with it
2- pressure increases with depth as the deeper you go into a liquid the weight is greater and the pressure increases
3- pressure depends on the density of the liquid, the denser the liquid the higher the pressure at any particular depth
4- pressure does not depend on the shape of the container, the pressure at any particular depth is the same.
what is a hydraulic machine
in some machines the forces are transmitted under pressure they are called hydraulic machines
why is a hydraulic jack called a force multiplier
because it multiplies the input force by a certain factor to gain a large output force.
why is the oil used instead of water?
oil is a natural lubricant/water evaporates but oil does not/ water will make the parts rust
a difference between air and liquid
air can be compressed but liquids can’t be compressed
explain barometer
it is used to measure the atmospheric pressure
what is the atmospheric pressure amount thingie
760 mm Hg
how much is 1 atm equal to
100,000Pa
what is the a) height of the mercury column b) gravitational field strength c) density of the mercury
a) 760mm/0.76m b)10N/kg c)13,590kg/m3
why is mercury used commonly in barometer and manometer
Mercury is commonly used in barometers because its high density means that the height of the column can be a reasonable size to measure atmospheric pressure
what is 1mb equal to
100Pa
what is boyles law
at a constant temperature, the pressure of the
gas is inversely proportional to the volume of the gas.
what is a manometer used for
The manometer is used to compare the pressure of a gas with the atmospheric pressure
what is excess pressure
The height difference
shows the extra pressure that the gas supply has in addition to
atmospheric pressure.
how do you find the actual pressure of the gas supply
add atmospheric
pressure to excess pressure. Standard atmospheric pressure is 1 atm.
how do you measure gas pressure
First measure the height difference of the liquid column. Then calculate the pressure difference of the liquid column(pgh). Pressure of the gas supply = pressure difference of the liquid
column + atmospheric pressure.
why does pressure increase when the volume decreases
the volume of the air trapped inside the
syringe decreases but the pressure of the air increases. The pressure
increases because the air molecules hit the wall of the syringe more
frequently.
what is Boyles law formula?
Initial pressure × initial volume = final pressure × final volume
(P1V1 = P2 V2)
