# Fluids

Contents

Atmospheric pressure is like an invisible friend who is always squeezing you with a big hug. Learn more about pressure, buoyant force, and flowing fluid so you can appreciate the sometimes invisible, but crucial, effect they have on us and the world around us.

## Density and Pressure

In these videos and articles you'll learn the definitions of density and specific gravity. You'll also learn the definition of pressure, how it relates to force and area, and how to determine the pressure within a fluid. The difference between absolute and gauge pressure will also be discussed.

3:10

Specific gravity

In this video David explains what specific gravity means. He also shows how to calculate the value for specific gravity and use it to determine the percent of an object that will be submerged while floating.

9:46

Pressure and Pascal's principle (part 1)

Sal explains the difference between liquids and gasses (both fluids). He then starts a calculation of the work done on a liquid in a U-shaped container.

10:12

Pressure and Pascal's principle (part 2)

Sal finishes the calculation or work to determine the mechanical advantage in a U-shaped tube. He also explains pressure and Pascal's Principal.

9:54

Pressure at a depth in a fluid

Sal derives the formula to determine the pressure at a specific depth in a fluid.

Article

What is pressure?

Pressure is kind of like force, but not quite.

10:09

Finding height of fluid in a barometer

Using our understanding of fluid pressure to figure out the height of a column of mercury.

## Buoyant Force and Archimedes' Principle

In these videos and articles you'll learn how pressure variations cause a buoyant force on a submerged object and how to calculate the value of the buoyant force. You'll also learn the meaning of Archimedes' principle.

8:41

Archimedes principle and buoyant force

Introduction to Archimedes' principle and buoyant force.

Article

What is buoyant force?

Why the heck do things float?

9:41

Buoyant force example problems

A couple of problems involving Archimedes' principle and buoyant forces.

## Fluid Dynamics

Flowing fluids behave different from static fluids. In these videos and articles you'll learn about volume flow rate and the equation of continuity. You'll also learn how Bernoulli's principle and Bernoulli's equation relate the pressure and speed of a flowing fluid. The effects of turbulence and viscosity will also be discussed.

9:59

Volume flow rate and equation of continuity

Sal introduces the notion of moving fluids and laminar flow. Then he uses the incompressibility of a liquid to show that the volume flow rate (flux) must remain constant. Sal then derives the equation of continuity in terms of the area and speed.

Article

What is volume flow rate?

You know all about the motion of individual objects. Now, let's talk about how to analyze the motion of a fluid.

10:08

Bernoulli's equation (part 1)

This is the first of two videos where Sal derives Bernoulli's equation.

10:09

Bernoulli's equation (part 2)

This is the second of two videos where Sal derives Bernoulli's equation. In the second half of the video Sal also begins an example problem where liquid exits a hole in a container.

8:35

Bernoulli's equation (part 3)

Sal finishes the example problem where liquid exits a hole in a container.

5:19

Bernoulli's equation (part 4)

Clarification of, and more thoughts on, the Bernoulli's equation example problem where liquid exits a hole in a container.

7:46

Bernoulli's example problem

Sal solves a Bernoulli's equation example problem where fluid is moving through a pipe of varying diameter.

Article

What is Bernoulli's equation?

This equation will give you the powers to analyze a fluid flowing up and down through all kinds of different tubes.

11:06

Viscosity and Poiseuille flow

David explains the concept of viscosity, viscous force, and Poiseuille's law.

2:10

Turbulence at high velocities and Reynold's number

In this video David explains how the Reynold's number allows you to determine the speed at which fluid flow becomes turbulent.

9:58

Venturi effect and Pitot tubes

David explains the Venturi effect and the role and function of Pitot tubes.

6:38

Surface Tension and Adhesion

David explains the concepts of surface tension, cohesion, and adhesion.