pressure Flashcards
What is pressure?
Pressure is the force per unit area. It is measured in Pascals.
How is pressure calculated?
Pressure (Pa) = force (N) ÷ area (m²)
What causes pressure in fluids?
Pressure is caused by particles colliding with the walls of the container, exerting a force.
What does pressure in fluids cause?
The pressure in fluids causes a force normal (at right angles) to any surface.
What is atmospheric pressure?
The atmosphere is a thin layer of air around the earth.
Where is the atmosphere most dense?
The atmosphere around the earth is most dense at the surface.
How does atmospheric pressure change with altitude?
The atmosphere gets less dense with increasing altitude.
What creates atmospheric pressure?
Air molecules colliding with the earth’s surface creates atmospheric pressure.
How does atmospheric pressure change with height?
As the surface above ground level increases height, the number of air molecules decreases, therefore, the atmospheric pressure decreases with an increase in height.
How is pressure due to a column of liquid calculated?
Pressure (Pa) = height of the column (m) × density of the liquid (kg/m³) × gravitational field strength (N/kg)
How does pressure change with depth in a liquid?
Water at the bottom of the container has a higher pressure than at the top. The pressure of a liquid increases with depth.
What affects liquid pressure?
The pressure of a liquid increases with density, as liquids with greater density have a greater weight acting downwards.
What is upthrust?
A partially (or totally) submerged object experiences a greater pressure on the bottom surface than on the top surface.
Why does upthrust occur?
This is because the bottom surface has a greater depth than the top, creating a larger force acting upwards.
What condition allows an object to float?
For an object to float, the upthrust must equal the object’s weight (downward force due to gravity).
What happens if weight is greater than upthrust?
If the weight is greater than the upthrust, the object sinks.
What is the relationship between upthrust and displaced water?
The size of the upthrust acting on the object is the same as the weight of water displaced by the object.
What happens when an object displaces its own weight of water?
If the object displaces its own weight of water, the upthrust will equal the object’s weight, and the object will float.
What is true for objects less dense than water?
Objects less dense than water only need to displace a small amount of water for it to float.
What is true for objects the same density as water?
Objects the same density as water need to displace their own weight of water.
What happens to objects more dense than water?
Objects more dense than water cannot displace a volume of water equal to their own weight, so they sink.
