Pressure, Pressure Difference in Fluids and Pressure in Gases Flashcards
What is pressure?
- force per unit area
What does the pressure in a fluid cause?
- a normal force (force at right angle) to act at any surface it touches
What can a fluid be?
liquid or gas
How do you calculate the pressure at the surface of a fluid?
pressure = force normal to a surface/ area of that surface
p = F / A
P = Pa
F = N
A = m^2
In what direction does the pressure in a fluid act in?
all directions
What is the relationship between the pressure of a liquid and depth?
also density
- larger depth = higher pressure
- higher density liquid with same depth > lower density liquid
- density of liquid higher = mass of liquid higher
How do you calculate the pressure in a column of liquid?
𝑝 = h x p x g
𝑝 = pressure in Pa
h = height in m
p = density in kg/m^2
g = N/kg
Describe the pressure in a fully or partially immersed object in a fluid
- greater pressure on bottom surface than on its top surface
- pressure increases with depth of fluid
- resultant force created = upthrust
How does an object float?
- upthrust greater than or equal to weight
- object has lower density than water
- weight of water > weight of object
How does an object sink?
- upthrust less than weight
- object has higher density than water
- weight of object > weight of water
What happens when an object is placed in water?
- displaces volume of water = volume of object in water
What is the relationship between the weight of the displaced water to the upthrust acting on the object?
- weight of displaced water = upthrust acting on object
What is the atmosphere?
- thin layer (compared to size of earth) of air around the Earth
- less dense with increasing altitude
What is atmospheric pressure caused by?
- air molecules collding with surface
