Pressure Flashcards
What is pressure?
The force exerted perpendicularly per unit area
Formula for pressure
Force/Area
What are the units for pressure?
N/m2 or Pa (Pascal) or cmHg (for pressure in air)
Why does a nail have a pointed end?
A small force will be required to drive the nail into a wall
Formula for pressure in liquids
Depth of object x density of liquid x gravity (10m/s2)
What does the pressure in liquids depend on?
Density and depth of object
What is atmospheric pressure?
It is the pressure exerted by air molecules on the Earth surface
What is the value of atmospheric pressure?
103000Pa or 76cmHg
Why does air pressure decrease with altitude?
Because there are less air molecules
Why does our nose bleed sometimes when we climb a moutain?
At the top, air pressure is less than pressure inside our body and therefore blood moves from high pressure to low pressure
What is used to measure air pressure?
A mercury barometer
What is a mercury manometer used for?
It is used to measure pressure of a gas in a cylinder or air in a tyre
What formula applies to gas when the temperature constant?
P1V1 = P2V2
Why shouldn’t a hot air balloon be fully inflated before taking off?
When the balloon moves up, air pressure will decrease and the volume of the balloon will increase because the pressure inside will be relatively greater.
If the hot air balloon is fully inflated before take off, the balloon will burst when it is up in the air
