P11 - Pressure in liquids and gases Flashcards
paper 2
What is a fluid?
a substance that can flow (liquid or gas)
What is the unit of pressure that is equal to one newton per square metre?
pascal (Pa)
Why does the pressure in a liquid increase with depth?
pressure at any point in a liquid is due to the weight of the liquid above that point.
Why does the pressure in a liquid depend on the density of the liquid?
pressure is due to the weight of the liquid and the weight of the liquid depends on the density
What is upthrust?
the resultant force due to the difference in pressure between the top and bottom surfaces of an object submerged in a fluid.
What will an object placed in a fluid do if its weight is equal to the upthrust?
float
What will an object placed in a fluid do if its weight is greater than the upthrust?
sink
Why does an object that is more dense than a fluid sink if it is placed in the fluid?
weight of the object is greater than the weight of the fluid displaced, so the wight of the object is greater than the upthrust
Why does an object that is less dense than a fluid float if it is placed in the fluid?
weight of the object is less than the weight of the fluid displaced, so the weight of the object is less than the upthrust
Does an object that is partially submerged in a fluid experience a greater pressure on its bottom or top surface?
bottom
What is the Earth’s atmosphere?
The layer of air that surrounds the earth
What is atmospheric pressure caused by?
air molecules colliding with surfaces
Why does atmospheric pressure decrease with increased altitude?
the density of the air decreases, fewer air molecules as you go higher - there is less weight of air above a surface and fewer air molecules so density of the atmosphere decreases
How does the height of the atmosphere compare to the radius of the earth?
it is smaller
