11 Flashcards
what is pressure caused by
when 2 objects exert a force on each other or when a fluid exerts a force on an object in contact with the fluid.
why do caterpillar tracks on vehicles help them in sandy/muddy/snow ground
they spread the weight of the vehicle reducing the pressure
pressure definition
force per unit area
pressure unit
pascal (Pa)
what is one pascal equal to
one newton per square metre (N/m3)
pressure equation
pressure = force/area
why does a sharp knife have a bugger cutting effect than a blunt one (same force)
It has a smaller area which means there is a bigger pressure
what happens to pressure of water with depth
increases
what does the pressure of a liquid depend on
density
what does a greater density of liquid mean
greater pressure
In a liquid what must the pressure be a horizonal points
equal
explain this
Oil is less dense that water, this means it will create a lower pressure. Since the pressure at horizonal points X and Y must be equal, there needs to be more oil to create an equal pressure.
what is the equation for the pressure at the bottom of a column of liquid
pressure=heightdensitygravitational potential field strength
what does the atmosphere do to the earth , and give a number for this
exerts a pressure on it. 100,000N at sea level
what is atmospheric pressure due to
air molecules colliding with surfaces
what happens to the density of the atmosphere with increasing height
decreases
what determines density of air
the weight of the air above a given point pushing down, compressing the air below.
why does density decrease with higher altitude
As you go higher there is less air above, so there is less weight of air pressing down. This means particles are not compressed, making it less dense.
why does a suction cup work
it removes the air between the cup and the wall. This means that that atmospheric pressure acts on the outside of the cup but not the inside. Making it stick to the wall.
why does a straw work
when you suck you remove air above the liquid, without any atmospheric above the liquid, the pressure acting on the liquid outside the straw pushes it up.
what happens to oxygen concentration with increasing altitude
decreases
what force does water exert on the body
upthrust
why does the water level rise when an object is lowered into a container
the object displaces water
what happens the more an object is lowered into water
the bigger the volume of water it displaces and the bigger the upthrust
what happens when an object is fully immersed in water
volume of water displaces is equal to the volume of the object
why is upthrust greater than the downward force of an object immersed in water
pressure is greater with greater depth of water, so pressure at the bottom of the object is higher
what does a ship do to water when its load is increased, and what is this effect
it displaces more, it increases the upthrust
what causes a ship to sink when being loaded
it has displaced as much water as it possibly can, and the upthrust is now lower than the weight
when does an object float
when its weight is equal to the upthrust
when does an object sink
when its weight is greater than the upthrust
what is the density of objects that float
less than water
what is the density of objects that sink
greater then water
what is upthrust equal to
weight of liquid displaced
why does an object that is more dense than liquid sink
because its weight is greater than the weight of liquid displaced. So the weight of the object is greater than the upthrust on the object when it is fully immersed.
why does an object less dense than the liquid float
its weight is less than the weight of liquid it displaces. So the weight of the object is less than the upthrust on the object when it is fully immersed.
