Unit 1: Fluids - Pressure and Forces

Density

\________ is a positive scalar quantity.

Density

Mass per unit volume of a substance is defined as density.

Buoyancy

If a body is fully or partially immersed in a fluid, it experiences an upward force due to the fluid called buoyant force, and the phenomenon is called buoyancy.

The Volume Flow Rate

It is the volume of fluid that passes through a particular point per unit of time.

f = Av

• f = volumetric flow rate

• A = cross-sectional area

• v = flow velocity v

Bernoulli’s Effect

At comparable heights, the pressure is lower where the flow speed is greater.

Air Flow

The air on the bottom has greater pressure and pushes up on the wing giving the airplane lift force

Pressure

Pressure is defined as the magnitude of the normal force acting per unit surface area.

P = F/A

• P is pressure

• F is force

• A is the area

Pressure units

Pascal (Pa) 1 Pa = 1 N/m^2

Practical units: atm, bar, torr

Hydrostatic pressure

It is the pressure due to the liquid.

Continuity equation

The density of the fluid is constant.

A1V1 = A2V2

• A1 and A2 (cross-sectional areas)

• V1 and V2 (flow velocities)

Bernoulli’s Equation (Conservation of energy in liquids)

• fluid is incompressible.

• fluid’s viscosity is negligible.

• fluid is streamlined.

• the equation is very similar to the conservation of energy with total mechanical energy.