12.1 Pressure Flashcards
What is pressure defined as?
Force/area
What are the units of pressure?
Nm^-2 or Pa
What is a pascal?
Pressure exerted by a force of 1N at right angles to an area of 1m^2
What is the equation for density?
density = mass/volume
What is the definition of pressure?
It is the force per unit area.
What are fluids? What states of matter does this include?
Substances that can flow, includes gases and liquids
What do you feel when you’re at the bottom of the pool and why?
Water pressure pushing onto your ears
What is this pressure created by?
the weight of the fluid(water in this case) above you
What is the atmospheric pressure?
101kPa at surface
What is the definition of atmospheric pressure?
the pressure exerted by the weight of the atmosphere
Why isn’t atmospheric pressure always 101kPa?
As this is a mean value, it changes all the time
What is the equation for pressure due to being in a fluid?
p = hpg
What does each symbol stand for and what are the units of each?
p = pressure (Nm^-2 or Pa) h = depth from surface of fluid ρ = density of fluid g = gravitational field strength (Nkg^-1)
What kind of fluids do we use this eqution for? (p = hρg)
Liquids
How do we derive this equation from the base equation for pressure (force/area)
Pressure at base = weight of column of liquid/area = F/a F/a = mg/a since m = ρV (density x volume) pVg/a since volume = h x a phag/a hence we get phg = p
Why isn’t p = hρg total pressure?
As atmospheric pressure of the air isn’t taken into account.
What is the equation for total pressure?
pt = pa + hpg
When liquids are stationary is pressure acting equally in all directions?why
Yes, otherwise there would be liquid flowing due to there being a resultant force (NEWTONS 1ST LAW)
What is 1atm?
101kPa
What is 101kPa in Pa?
101000
