Angular Momentum What is it? by Sadeeque Mohamed } The quantity of rotation of a body, which is the product of its moment of inertia and its angular velocity. Angular Momentum is... — From the New Oxford American Dictionary } Wait, What? Two important concepts:

2) angular velocity 1) rotational inertia Rotational Inertia INERTIA comes from the root inert-, or inactive, and it means the quality of something to resist a change in motion - in this case, matter! } } A property of all matter is inertia, and the more massive an object, the more inertia it has. This is why you can pull a tablecloth out from under glasses and plates, because they resist a change in motion with the tablecloth enough to stay where they are. } ROTATIONAL inertia is the same idea as inertia, except it has to do with things moving around a center axis. Rotational inertia of a pendulum is equal to the mass of the pendulum times the lever arm distance squared, or I=mr and this is why it is harder balance a short pole than a long pole on your palm. 2 Angular Velocity Angular velocity, also known as rotational speed, is the amount of rotations an object makes around an axis per a given period of time. It is expressed with the lowercase omega symbol, , and it is equal to the linear velocity of the object divided by the radial arm distance. > Multiply these two properties of a rotating body together and you get the object's angular momentum! Angular momentum is like linear momentum in that they are both relations to mass and velocity, but angular momentum is related to rotational inertia and velocity, whereas velocity is linear in linear momentum. And that's exactly what momentum is: moving inertia. An object resists change in velocity when it is moving or not, and it is called momentum when the object is moving. } The quality of an object to resist changing its rotation around an axis expressed as

(its rotational inertia) x (its rotational velocity) IN SUMMARY, what is angular momentum? Easy to Rotate Hard to Rotate A good example of the contrast between linear and angular velocity is the difference between the speed of the equator as opposed to the poles of the earth. While it takes a day for both to make one rotation around the earth's axis, they move at vastly different linear speeds. The reason why gyroscopes can maintain such weird and magical positions for extended periods of time is because their rotational momentum resists the force of gravity for quite a while... Well, hope this was a good review that hopefully will get me an A in the class.

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# Angular Momentum - What is it?

A short description of Angular Momentum by Andrew Biehl

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