P11: Pressure And Surfaces Flashcards
What is pressure?
Pressure is the force per unit area
How os pressure calculated?
Pressure (N/m^2) = Force(N)/ Area (m^2)
How can the area of a circle be calcualted?
Pi x r^2
How is mass converted to force?
F = m x gravitational force
What container will have the greatest pressure at its base?
Has the greatest mass above the base and therefore weight (force) applied to the area of the base for the container- this will result in the greatest pressure experienced
Why may water travel further in a hole further to the base of a container of water?
The pressure of the liquid increases with depth (height). The further the hole is below the surface of the water the greater the force of the jet leaving the water bottle.
How can pressure be calculated?
P = density (kg/m^3) x gravity (N/kg or m/s^2) x height (m)
Why does a water dam have a thicker base than top- triangle shape?
The greater the depth of the water the greater the pressure of water against the dam wall – this greater pressure requires a greater structure to safely hold the water back without breaking.
How do straws work?
When you suck on a straw, you remove air from inside it, creating lower pressure. The atmospheric air pressure outside the straw is greater and forces the liquid up the straw; liquids move from areas of higher pressure to lower pressure.
What is atmospheric pressure?
Air pressure is caused by the force of air gas particles bumping into things. (+ Weight of the air particles pressing down.) Air pressure is equal in all directions.
What is the unit for pressure?
Pa
How does atmospheric pressure change with elevation above sea level?
As the elevation above sea level increases, the amount of air above given point decreases, therefore decreasing the pressure
In what direction does atmospheric pressure act in?
All directions
Why may a seal packet of crisps be found blown up like a balloon at the top of the mountain?
the air outside is now at a lower pressure than the air inside the packet.
What is atmospheric pressure equal to at sea level?
101,300 Pa
What is upthrust?
Upthrust is the upward force that a fluid (liquid or gas) exerts on a body (or object) floating in it.
What happens when an object is placed in water?
When an object is lowered into water, it displaces (moves) some of the water.
• The more the object is lowered into the water, the greater the amount (or volume) of water displaced.
• A fully immersed object displaces an equal volume of water as the object.
What is archimedes’ principle?
An object totally or partially immersed in a fluid is subject to an upward force (upthrust) equal in magnitude (size) to the weight of fluid it displaces.
What happens when an object floats?
An object floats when its weight is Equal to the upthrust provided by the fluid.
What happens when an object sinks?
An object sinks when its weight is greater than upthrust provided by the fluid.
How do you calculate mass?
m= density x volume
What is the pressure difference between top and bottom of the object?
The height difference determines the overall pressure difference between the top and bottom of the object.
Hw is the pressure difference between top and bottom calculated?
Change in pressure = density x gravity x change in height
How is mass calculated?
Mass = Volume x density
How is force (upthrust) calculated?
F = Density x gravity x volume
What is the density of water?
1000kg/m^3
