Fluids Flashcards
definition of pressure.
P= A/F
Key idea: Pressure increases when you apply more force over a smaller area (e.g., a needle tip).
Mnemonic: “Force over Area equals Pressure.”
Poiseuille’s Law: Used to calculate the volume flow rate in the case of laminar flow
Q = volume flow rate in m3/s
r = radius of vessel in m
ΔP = change in pressure in Pa
η = fluid viscosity in Pa*s
L = length of vessel in m
Formula for the buoyant force on an object in a fluid
Fb = buoyant force in N
𝜌 = density of fluid in kg/m3
V = volume of fluid displaced in m3
g = gravitational acceleration = 10 m/s2 on Earth
Key idea: Objects float if the buoyant force matches their weight.
Mnemonic: “Float with Rho V G.”
Volume Flow Rate: Used to measure the amount of fluid volume that passes through an area per time
Q = volume flow rate in m3/s
A = cross sectional area of the fluid in m2
v = fluid velocity in m/s
Key idea: If a pipe narrows, velocity increases to keep flow rate constant.
Mnemonic: “Quick AV pipes flow.”
Fluid Density: It tells you how much matter is packed into a given space.
𝜌 = density in kg/m3
m = mass in kg
V = volume in m3
Key idea: Materials with high density (like lead) have more mass in the same volume compared to low-density materials (like air).
Mnemonic: “Dense Milk in a Volume” — Think of dense milk filling a container.
Bernoulli’s Equation
P1, P2 = hydrostatic pressure in Pa
𝜌 = fluid density in kg/m3
v1, v2 = fluid velocity in m/s
g = gravitational acceleration = 10 m/s2
What it means: In a steady flow, the sum of pressure energy (P), gravitational potential energy (ρgh), and kinetic energy per volume (1/2𝜌𝑣2) is constant.
Key idea: High speed means lower pressure (think of air moving over airplane wings).
Mnemonic: “Bernoulli Packs Gravity, Pressure, Velocity.”
Hydrostatic Pressure: Formula to “gauge” the hydrostatic pressure of a column of liquid
P = hydrostatic pressure in Pa
𝜌 = fluid density in kg/m3
g = gravitational acceleration = 10 m/s2 on Earth
h = depth of fluid in m
Pascal’s Law: Used to calculate force or cross-sectional area of hydrostatics when differing cross-sectional areas are used to provide a mechanical advantage.
F1 = force applied to 1st location
A1 = cross-sectional area of fluid at 1st location
F2 = force transferred to 2nd location
A2 = cross-sectional area of fluid at 2nd location
Hydrostatic Pressure: When you want the “absolute” pressure at a depth in a fluid,
Key idea: The deeper you go, the more pressure you experience because of the weight of the fluid above you.
Mnemonic: “Pressure adds up with depth.”
