Atmospheric Pressure

2.2

Atmospheric Pressure

	Atmospheric pressure
	Pressure due to the weight of the layer of air acting on the surface of the Earth.

Instruments to measure atmospheric pressure

Applications of atmospheric pressure

Drinking straw
- When straw is sucked, the air velocity in straw is high
- The air pressure in the straw is lower than atmospheric pressure
- Air is pushed up into a straw by atmospheric pressure
Rubber sucker
- When the rubber is pressed, the air is removed
- There is low pressure inside rubber sucker (partial vacuum)
- Atmospheric pressure is higher than pressure inside rubber
- Rubber sucker sticks on surface
Siphon
- Atmospheric pressure is higher than the pressure in the siphone
- The atmospheric pressure acting on liquid push the liquid down to a lower container
Syringes
- When the piston is pulled, the pressure in the syringe decreases
- The pressure in the syringe is lower than atmospheric pressure
- The atmospheric pressure at the surface force water into the syringe.
Vacuum cleaner
- Vacuum fan removes air from space inside dust bag
- The pressure in the dust bag is lower than atmospheric pressure
- Outside air is sucked into the dust bag together with dusts

2.2

Atmospheric Pressure

	Atmospheric pressure
	Pressure due to the weight of the layer of air acting on the surface of the Earth.

Instruments to measure atmospheric pressure

Applications of atmospheric pressure

Drinking straw
- When straw is sucked, the air velocity in straw is high
- The air pressure in the straw is lower than atmospheric pressure
- Air is pushed up into a straw by atmospheric pressure
Rubber sucker
- When the rubber is pressed, the air is removed
- There is low pressure inside rubber sucker (partial vacuum)
- Atmospheric pressure is higher than pressure inside rubber
- Rubber sucker sticks on surface
Siphon
- Atmospheric pressure is higher than the pressure in the siphone
- The atmospheric pressure acting on liquid push the liquid down to a lower container
Syringes
- When the piston is pulled, the pressure in the syringe decreases
- The pressure in the syringe is lower than atmospheric pressure
- The atmospheric pressure at the surface force water into the syringe.
Vacuum cleaner
- Vacuum fan removes air from space inside dust bag
- The pressure in the dust bag is lower than atmospheric pressure
- Outside air is sucked into the dust bag together with dusts