Angular Momentum

Source: Nicholas Timmons, Asantha Cooray, PhD, Department of Physics & Astronomy, School of Physical Sciences, University of California, Irvine, CA

Angular momentum is defined as the product of the moment of inertia and the angular velocity of the object. Like its linear analog, angular momentum is conserved, meaning that the total angular momentum of a system will not change if there are no external torques on the system. A torque is the rotational equivalent of a force. Because it is a conserved, angular momentum is an important quantity in physics.

The goal of this experiment is to measure the angular momentum of a rotating rod and to use the conservation of angular momentum to explain two rotational demonstrations.

1. Test the theory of the conservation of angular momentum with the bike wheel.

While sitting in a chair that can freely rotate, start spinning the bike wheel and then hold it by the handles so that its direction of angular momentum is vertical.
While holding the wheel by the two handles, flip the wheel over so that its angular momentum points in the opposite direction. Notice how the chair will begin to rotate.

2. Test the theory of the conservation of angular momen

Mass (g)	Angular momentum at halfway (kg m²)/s	Angular momentum at bottom (kg m²)/s	Difference (kg m²)/s
200	0.41	0.58	0.17
500	0.66	0.91	0.25
1,000	0.93	Log in or to access full content. Learn more about your institution’s access to JoVE content here Just like in the spinning chair portion of the lab, changing the moment of inertia of an object can increase or decrease the angular velocity of that object. Figure skaters take advantage of this and will sometimes begin spinning with their arms outstretched and then bring their arms in close to their bodies, which will make them spin much faster. Why is it easier to balance on a bike when it is in motion? The answer is angular momentum. When the wheels are not spinning, it is easy for Log in or to access full content. Learn more about your institution’s access to JoVE content here A spinning mass has the property of angular momentum and conservation of angular momentum is central to solving problems in rotational dynamics. As explained in another video of this collection, an object's linear momentum does not change, that is Δp is zero until a net external force is applied. The same conservation principle applies to angular momentum, denoted by the letter L. So ΔL is also zero until a net external torque is applied. Here, we will first explain the concept of angular momentum and show how it is conser Log in or to access full content. Learn more about your institution’s access to JoVE content here Explore More Videos Angular Momentum Conservation Of Angular Momentum Rotational Dynamics Linear Momentum Net External Force Net External Torque Spinning Mass Rotational Motion Radius Translational Momentum Tangential Velocity Angular Velocity Right hand Rule Privacy Terms of Use Policies Contact Us Recommend to library JoVE NEWSLETTERS Research JoVE Journal Methods Collections JoVE Encyclopedia of Experiments Archive Education JoVE Core JoVE Business JoVE Science Education JoVE Lab Manual Faculty Resource Center Faculty Site Authors Overview Publishing Process Editorial Board Scope and Policies Peer Review FAQ Submit Librarians Overview Testimonials Subscriptions Access Resources Library Advisory Board FAQ ABOUT JoVE Overview Leadership Blog Copyright © 2024 MyJoVE Corporation. All rights reserved