Pressure Flashcards
(30 cards)
Pressure
The force per unit area
Pressure formula
Pressure (Pa or Pascal) = Force / Area
Or
P = F/A
1Pa =
1 N/m^2
Sometimes N/cm^2 is used if you cannot convert.
1N/cm^2 =
10000 Pa
Can you use recurring decimals?
No
How does a gas exert pressure?
In a sealed container, gas particles collide with the sides of the container, exerting a force on it, causing pressure. This movement is due to the pressure difference from the high pressure in the container, to the low pressure outside.
What pressure is there at ground level?
Greater pressure due to higher density. There is low pressure in the air (eg. ears pop on a plane, mountain climbers bring oxygen tanks when at high altitude)
What is atmospheric pressure?
Pressure exerted on us by the air around us
Do fluids cause pressure?
Yes, as particles collisions exert a force on objects, and P = F/A.
What is 1 atm?
The atmospheric pressure at sea level
1atm =
100,000 Pa
1mbar =
100Pa
Calculating pressure in a fluid
Fluid pressure = density x gravitational field strength x depth
P = ρgh
If you keep density to kg/m^3 and depth in m, then the pressure will be in Pascals (Pa).
How does pressure at a point in a gas or liquid act?
Equally in all directions
Which exerts more pressure - saltwater or fresh water?
Saltwater, as it is more dense, having dissolved salt particles, and P = ρgh, increasing pressure.
Density of water
1000 kg/m^3
Density of mercury
13,500 kg/m^3
What happens when a bubble rises in a liquid?
As a bubble rises in a liquid, the external pressure acting on the bubble due to the water (P = ρgh) decreases, while the internal pressure of the gas in the bubble remains constant. Hence, the internal pressure is able to overcome the external pressure, expanding in size as it rises.
Pressure in space is…
0Pa
What is the total pressure of the person in a fluid?
The total pressure on a person in a fluid includes atmospheric and liquid pressure.
P(total) = P(liquid) + P(atmospheric)
The equation P = ρgh only give you the pressure difference once in the fluid, not the total pressure, which includes atmospheric pressure.
What happens when gases are compressed in a container?
There is an increased frequency or collisions against the side of the container, as there is even less space for the gas particle movement, increasing pressure
What is a manometer?
A manometer is a U-shaped tube that uses a reference liquid to find the pressure difference between a gas inlet and atmospheric pressure, allowing us to find the pressure on the gas pipe.
The gas has enough pressure to support the column of liquid, and the atmosphere.
Draw the bubble rising
N/a
Explain how a manometer works
A manometer is a U-shaped tube filled with liquid (like water or mercury) used to measure gas pressure. One end is connected to the gas, and the other is open to the air or another gas. When gas pressure is applied, it pushes the liquid down on one side, causing it to rise on the other. The difference in height between the two sides shows how strong the gas pressure is. This height can be measured in units like cm of water, which tells you how much pressure is needed to support that height of liquid.
