Tornadoes, hurricanes, whirlpools, and water going down the drain all contain of a vortex. The video demonstrates how to create two vortices that travel together the length of a swimming pool. It explains the physics behind the concept...

Amaze your class with this demonstration of gravity and friction. A ring on a string is able to catch a spool of tape as it falls. This is a perfect introduction for a class discussion on these topics, or you could have kids them try it...

How do satellites orbit the earth? Technically they are free-falling, but missing Earth's surface! Being explained in great detail and with entertaining animation, these concepts are sure to amaze your starling scientists! Another plus...

On June 7, 1692, at 11:43 am, the Jamaican city of Port Royal sank into the harbor, killing more than 2,000 people. The video explains this disaster and others that were caused by liquefaction, describes the conditions required, and...

Sal Khan explains how a block of wood is kept stationary by the force of friction (correction made in next video). [8:40]

A block of wood is kept stationary by the force of friction. (A correction to this video is made in the next video.) [8:41]

Sal Khan demonstrates how to calculate the coefficient of kinetic friction (correction made in next video). [9:08]

Calculate the coefficient of kinetic friction for a block that is on an incline plane with this video lecture. Video includes a step-by-step process for solving these types of problems. [9:09]

Corrects an numerical error in a previous video on how a block of wood is kept stationary by the force of friction.

Tires on a car in a NASCAR race are filled with nitrogen. The force of friction increases tire pressure as the car goes around the track. Using dry nitrogen gas helps with predicting the temperature and pressure of a tire during a race....

Students move past the misconception that friction inhibits our ability to do things by watching videos and participating in corresponding activities. Activities which range in difficulty include calculating the coefficient of friction.

A video lesson explaining how tension forces can be used to determine the force of friction acting on an object. [6:33]

In this video David shows how to find the energy generated by the force of friction and solves an example conservation of energy problem involving thermal energy. [14:47]

An analysis of the components of the force due to gravity that are parallel and perpendicular to the surface of an inclined plane. [12:43]

Understand how force, acceleration, gravity, friction, and wind resistance all relate to the exciting sport of alpine skiing. [4:00]

Friction always creates heat. Brakes and tires depend on friction to work, while the opposite is true of an engine. Engine builders use oil and high-tech coatings to get more power from an engine. [5:25]

In this video lecture, the topics of static and kinetic friction are explored with examples. The video discusses free-body diagrams and the forces that affect the movement of objects. [9:49]

The second part to a complicated problem. We figure out the tension in the wire connecting two masses. Then we figure our how much we need to accelerate a pie for it to safely reach a man's face. [9:28]

This lesson demonstrates how tension forces can be used to determine the friction force acting on an object. It is 1 of 2 in the series titled "Tension Forces & Friction."

This lesson introduces the concept of friction and explains how it interacts with objects. It is 2 of 2 in the series titled "Introduction to Friction."

Success in auto racing depends on the grip of a car's tires. Grip is the frictional force that holds the tires on the track. Aerodynamic features of a car also improve a car's grip. [5:02]

A video lesson investigating how frictional forces are involved in almost all of your everyday activities. Understand that the resistance you feel when sliding objects past each other or moving objects through water and air is friction....

This lesson explains the difference between static and kinetic friction. It is 1 of 2 in the series titled "Static & Kinetic Friction." [6:58]

This video covers the basics of gravity and the Law of Universal Gravitation. [15:42]