8 pressure my ass to study i dont think so Flashcards
Effect of force acting on surface depends on
Surface area of which the force is applied
What is pressure
Force per unit area (direction of force is perpendicular to surface area)
What is the formula for pressure & SI unit
Force (N) / Surface area (m^2)
pascal (Pa)
1 Pa = 1 newton per square metre
What does the kinetic theory of gas relate to air pressure
Air molecules always move about freely & collide w/ walls of its container
The frequency of collision -> force that pauses against the walls = air pressure
Factors affecting air pressure
Volume
Temperature
State relation between volume & air pressure
Closed container compressed -> volume reduced -> air particles collide more frequently w/ walls -> air pressure increases
What is used to measure air pressure
Bourdon gauge
What is relation between temperature and air pressure
Air temperature increase -> air particles move faster -> collide more frequently w/ walls -> greater force
When a drink is sucked out of its packet why will the packet compress
Drink inside packet becomes partial vacuum -> air pressure inside decrease
Higher air pressure outside -> press onto packet -> compress it
What is atmospheric pressure
Air pressure outside
Exerted by atmosphere on surface of Earth & all objects on Earth
What is the principle of plunger
- Plunger pressed against sink -> air inside force out -> low pressure
- Pull up plunger -> high pressure in pipe pushes out stuck blockage
What is the principle of Magdeburg Hemisphere
- Air in hemisphere pumped out -> space becomes vacuum (pressure = 0)
- two hemisphere cannot be separated -> atmospheric pressure outside exert very strong force on hemisphere
What is the principle of a straw
- Air in straw is sucked -> pressure invide reduced
- Higher pressure outside -> push drink into straw -> into mouth
What is the principle of syphon
- End of tube B -> lower than tube A -> water flow out
- Water flows out -> low air pressure in tube
- Atmospheric pressure pushes water into tube -> water flows out continuously
What is the principle of syringe
- Piston pulled up -> volume of air increases -> low air pressure in cylinder
- Higher air pressure outside push liquid into syringe
What is the principle of vacuum cleaner
- Switch on -> fan in vacuum push air out -> air pressure in vacuum cleaner drops
- High atmospheric pressure push air & dust into vacuum cleaner
Explain how to pour condensed milk out easy from a tin can
Make hole on top so air can flow through -> balance air pressure inside and outside
One hole- milk does not flow out easily -> high pressure outside can
Two holes- milk floes out easily-> air pressure inside & outside is equal
Other than making another hole, how to pour condense milk out
Repeatedly pour and put down to let the sir reenter
What is relation between atmospheric pressure and altitude
Ap decrease - altitude increase
Gravitational attraction - air molecules close to surface of earth are pulled together by GA -> pressure rise
Higher altitude -> air molecules less affected by GA -> less heavy & expands easily
Liquid pressure depends on
Depth
Why do bubbles become larger as they rise to surface
Decreasing liquid pressure as depth decreases
How are walls of dam designed
Thicker at base - withstand high water pressure at the base
Why to divers wear special suit
Withstand high water pressure
What is body of submarine made out of and why
Strong material
Will not be crushed by high water pressure
