6.2 Application of the Principle of Air Pressure

Success Criteria:OExplain with examples things

that use the principle of air pressure

OGenerate ideas to solve problems using the principle of air pressure

ORelate the safety to measures taken when using gas under high pressure

Appliances that use the principle of air pressure

OSyringe ODrinking with a straw ORubber sucker OSpraying pump OSiphoning water outOVacuum cleaner OFoot pump

When the piston is pulled up, the atmospheric pressure inside the cylinder will decrease. The atmospheric pressure outside pushes the liquid up into the syringe.

Syringe

When a person suck through the straw, the pressure in the straw become low.

The atmospheric pressure outside which is higher will force the water into the straw and consequently into the mouth.

Drinking with a straw

When the sucker is pressed into place, the air inside is forced out.

The sucker is held in position by the high atmospheric pressure on the outside surface.

Rubber sucker

The atmospheric pressure which is higher in magnitude, forces the air and duct particles into the cleaner.

When a vacuum cleaner is switched on, it sucks out the air inside the cleaner, causes the pressure inside the cleaner become low.

Vacuum cleaner

Siphoning Water Out

Using The Principle Of Air Pressure To Solve Daily Problem

OAir pressure is strong, and it exists all around us.

OWe can utilise the principle of air pressure when we understand it and it can benefit our lives.

Activity

OHow blockage in the drainage pipe of a sink can be removed

OHow to pour condensed milk out of a can

Gas under High Pressure

OGas tanks containing gas under high pressure are used in various places such as hospitals, factories, and vehicle workshops.

OLarge quantities of gas usually stored in liquid form in strong metal cylinder.

OSmall quantities of gas can be stored in small aerosol cans.

OAll these gases are stored under high pressure and liquefied.

OLiquefied gas can be turn into gas again once the pressure is release.

OExample of gases that are used in large quantities in many industries :

A) Hydrogen is used for welding and as a rocket fuel.

B) Oxygen is used in hospitals, diving, welding and rocket fuel.

C) Carbon dioxide is used in fire extinguishers and manufacturing of dry ice

D) Nitrogen is used to store fish at low temperature and in cooling system.

E) Liquefied Petroleum Gas (LPG) is used as fuel in homes and vehicles

OAn aerosol contains vapour under high pressure. This pressurised vapour acts as a propelling agent in driving the liquid contents out of the can as a spray.

OAerosols cans are mostly used to store and spray insecticides, perfumes, hair sprays, paints and etc.

O In motor workshops, air under high pressure is used to drive a wrench in loosening tight screws or nuts.

OA jet of air released at high speed is used to blow dust or water from engine parts.

Safety Measure When Using Gas Under high Pressure. ODo not place the tank near the

heat source

OAlways place the tank upright

ODo not dispose of aerosol can in a fire