Angular Momentum

Overview

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.

Procedure

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

Results

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 Application and Summary 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 Tags 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 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 momentum with two weights. While sitting in a chair that can freely rotate, hold two weights out at arm's length. Have a partner get the chair spinning and then bring the weights in close to the chest. Notice the increased speed of rotation of the chair. 3. Measure the change of angular momentum in the spinning rod. Measure the length of the rod and its mass. Using a meter stick, measure the halfway point of the falling weight and mark the vertical beam with tape in order to have a reference. Calculate the moment of inertia of the rod. Add 200 g to the end of the string and wind it up to the top. Take notice of where the halfway point of the string is located. Release the weight and measure the amount of time it takes to get to the halfway mark and then again to the bottom. Do this three times and take the average values. Calculate the angular momentum at both points. Increase the weight at the end of the string to 500 g and repeat step 3.3. Increase the weight to 1,000 g and repeat step 3.3. Skip to... 0:03 Overview 0:57 Principle of Angular Momentum Conservation 2:17 Demonstration of Angular Momentum Conservation 4:32 Measurement of Angular Momentum for a Spinning Rod 6:21 Data Analysis and Results 7:54 Applications 9:01 Summary Videos from this collection: Now Playing Angular Momentum Physics I 35.7K Views Newton's Laws of Motion Physics I 75.5K Views Force and Acceleration Physics I 78.8K Views Vectors in Multiple Directions Physics I 182.2K Views Kinematics and Projectile Motion Physics I 72.4K Views Newton's Law of Universal Gravitation Physics I 190.4K Views Conservation of Momentum Physics I 43.1K Views Friction Physics I 52.8K Views Hooke's Law and Simple Harmonic Motion Physics I 61.2K Views Equilibrium and Free-body Diagrams Physics I 37.3K Views Torque Physics I 24.2K Views Rotational Inertia Physics I 43.4K Views Energy and Work Physics I 49.6K Views Enthalpy Physics I 59.7K Views Entropy Physics I 17.5K Views 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 Science Education JoVE Lab Manual JoVE Business JoVE Quiz JoVE Playlist 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 JoVE Help Center JoVE Sitemap Copyright © 2025 MyJoVE Corporation. All rights reserved