4.5.5 Pressure and Pressure Differences in Fluids (will come up) P2 Flashcards
What is meant by the term fluid
A liquid or a gas
In any fluid, at what angle do the forces due to pressure act on a given surface
At right angles (normal to) the surface
Units for pressure
Pascals
What happens to the density of the atmosphere with increasing altitude
The atmosphere becomes less dense as the altitude decreases
Explain why atmospheric pressure decreases with an increase in height
Pressure is created by collisions of air molecules
The quantity of molecules decreases as height increases
This means atmospheric pressure decreases with an increase of height
What is the Earth’s atmosphere
A thin layer of gas surrounding the earth
How does pressure in fluids increase with depth
As depth increases, the mass of liquid above that depth also increases
This means that the force due to mass increases
Since the force has increased whilst the area has remained constant, the pressure will increase
Why does pressure in fluids increase with density
As the density of the fluid increases, the number of particles in a given volume increases
Consequently the weight of the fluid is greater
This means that the force from the fluid above a certain point is larger
Since the force has increased, the pressure has also increased
Why are objects in a fluid subject to an upthrust
When an object is submerged in a fluid, it has a higher pressure below it than it does above as there is more weight above it at the bottom than there is at the top
This leads to an upwards force called upthrust
You float or sink depending on whether the upthrust is more or less than your weight
What is upthrust always equal to
The weight of the fluid that the object displaces
What factors influence whether an object will sink or float
Upthrust
Weight
Density of fluid
Explain why an object with a density greater than that of water can never float
Upthrust is equal to the weight of the displaced fluid
If the density of the object is high, there would not be enough volume displaced to produce an upthrust larger than the objects weight
This means that it will sink
