Correction of definition of "normal force" and an introduction to the coefficient of friction. This video, which is suitable for high school students, starts with a black screen because the instructor, in his conversational tone, uses it as a 'chalkb...oard.' (09:25)[more]

Calculating the acceleration of on object sliding down an inclined plane with friction. This ten-minute video, which is suitable for high school students, starts with a black screen because the instructor, in his conversational tone, uses it as a 'ch...alkboard.'[more]

Fun with two masses, some wire, a pulley, and a ramp with friction. This video, which is suitable for high school students, starts with a black screen because the instructor, in his conversational tone, uses it as a 'chalkboard.' (10:15)

This is how you include air resistance in projectile motion. It requires the Drag Force and Numerical Modeling (or the Euler Method). It is also very helpful to use a spreadsheet to do the calculations. I prove a statement from a previous projecti...le motion problem video, "Air resistance decreases the x displacement of the ball by less than 1 cm."
Content Times:
0:22 The statement this video proves
1:01 The basic concept of air resistance
1:54 The Free Body Diagram
2:20 The Drag Force Equation
3:13 Information about the Lacrosse Ball
4:03 The Drag Coefficient
4:55 The Density of Air
5:18 How the Drag Force affects the motion
5:58 The basic idea of Numerical Modeling (or the Euler Method)
6:50 Solving for the acceleration in the x direction
8:53 Solving for the final velocity in the x direction
9:54 Solving for the final position in the x direction
11:41 Entering the Lacrosse Ball information into Excel
13:34 Solving for the Drag Force in x direction in Excel
14:29 Solving for the acceleration in the x direction in Excel
14:58 Solving for the final velocity and final position in the x direction in Excel
15:46 Solving for the acceleration in the y direction
17:21 Solving for all the variables in the y direction in Excel
19:13 Click and Drag Copy. Harnessing the Power of Excel!
19:43 Understanding the numbers in Excel
20:35 Solving for the decrease in the x displacement caused by the Drag Force
Want lecture notes & the Excel File?
The original problem videos for this are:
(part 1 of 2) An Introductory Projectile Motion Problem with an Initial Horizontal Velocity
(part 2 of 2) An Introductory Projectile Motion Problem with an Initial Horizontal Velocity
How Many Attempts did it Really Take? - with live music from Amos Lee
Next Problem: Nerd-A-Pult – An Introductory Projectile Motion Problem
1¢/minute[more]

If you hold your feet flat or point them, does it change how far you slide. This video shows the answer and explains why using the concept of drag force.
Content Times:
0:26 Showing the two foot positions
0:57 Defining aerodynamic
1:41 Defining... the Drag Force
2:32 A closer look at the cross sectional area
4:04 Showing the answer
5:05 Comparing splashes
5:43 A second demonstration
6:22 Many thanks
Multilingual? Please help translate Flipping Physics videos!
Another Drag Force Video: A Brief Look at the Force of Drag using Numerical Modeling (or The Euler Method)
Thank you Rhonda Petty of Rolling Hills Water Park
Thank you Aaron Fown of FirstUAV for the aerial footage.
1¢/minute[more]

Introduction to friction - Khan Academy Presents: Correction of definition of "normal force" and an introduction to the coefficient of friction. Mr. Khan uses computer software for demonstration. (09:24)

From nsf.gov, produced by National Science Foundation

This 5:25 long video shows how friction always creates heat in race cars. Brakes and tires depend on friction to work, but more friction isn't always better. In the engine, friction is never good and engine builders use everything from oil to high-t...ech coatings to get a little extra horsepower. A good lesson to show students how friction impact their life.[more]

Khan Academy Presents: Fun with two masses, some wire, a pulley, and a ramp with friction. (10:15) Sal Khan uses computer software and different colors for demonstration.

In this game, students participate in a race where they utilize their knowldege of friction, the force between two surfaces. ( This link is for an interactive game and may take a few mimutes to load.)

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