forces And Pressure Flashcards
(21 cards)
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 a liquid depends on its 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 weight of the object is greater 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 gases surrounding the planet.
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.
How does the height of the atmosphere compare to the radius of the Earth?
It is smaller.
What us upthrust equal to
The weight of the fluid that it displaces
Elastic vs plastic deformation
Elastic will return to its original shape and length once the force has been removed-plastic will not
What is the rate at which objects for due to?
Air resistance eg lighter objects for slower because they have more resistance 
Altitude definition
Height above the surface
How do you measure up thrust with a newton meter?
You measure weight of the object in water and then an air the difference is the upthrust
What happens when particles collide with a surface e.g. a container?
They exert a force
A-what happens to the pressure whilst the altitude increases?
B-what happens to the density whilst the altitude increases?
A-the pressure decreases
B-The density decreases
What happens to oxygen concentration as the altitude increases?
It lowers in concentration
