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Flashcards in Pressure And Density Deck (11):

What is density measured in?



How to work out pressure

Pressure = force/area


What is pressure measured in?

• N/cm²
• N/m² = Pa (pascal)


What three factors affect the pressure in a fluid?

• Depth the pressure is measured at (the greater the depth, the greater the pressure)
• Density of the fluid (the greater the density, the greater the pressure)
• Gravitational field strength (the greater the gravitational field strength, the greater the pressure)


What equation links all the three factors affecting pressure?

• pressure = depth x density of fluid x strength of gravity
• p(Pa=N/m²) = h(m) x p(kg/m³) x g(10N/kg)


Three holed can

• This can shoes that pressure in a fluid increases with depth.
• Top hole comes out slowest and travels the least distance across, but the bottom hole moves out fastest and travels furthest.


Magdeburg hemispheres

• Two metal cups that fit together. If most of the air is removed from inside them using a vacuum pump, it's nearly impossible to pull them apart.
• The pressure of the atmosphere acting on their outside surfaces pushes them tightly together - there is no pressure on the inside because there is no air.
• Once air is let back in, the pressure inside equals the pressure outside and the cups can be easily separated.


Collapsing can

• Water is boiled in an empty drinks can.
• When the water has boiled, steam fills the can.
• If the can is then turned upside down in a trough of cold water, the steam condenses and the air pressure inside goes down - causing the can to collapse due to the pressure of the air outside.


How to work out density

Density = mass/volume


Why does air pressure decrease the higher up you go?

• Atmospheric density increases the higher up you go.
• Air is colder higher up, so the molecules are moving less slowly.


How does a decrease in air pressure outside a ballon affect the hot air inside it?

• The balloon expands.
• Air escapes from the ballon.
• The hot air cools down.