Rotational Inertia/Angular Momentum & Center of Mass/Gravity

This video is about Rotational Inertia and Angular Momentum. I like this video for multiple reason; it makes the definitions easy to understand, teenagers created it and it has examples that we have used in class, both of which make it relatable. Rotational inertia is the amount of resistance an object has to rotate. The video related rotation inertia to mass by saying, "rotational inertia depends on where the concentration of mass is. If it is close to the axis of rotation, it will have a small inertia and if it is far away, it will have a big inertia". I thought inertia was how big the object was, but that definition really cleared it up for me. The video also made clear that rotational inertia and rotational velocity are inversely proportional to each other, which makes the conservation of angular momentum law make sense (angular momentum before=angular momentum after). I found this video very useful.


This video explains the center of mass through acceleration and numbers, so if you wanted to know exactly how to solve for the center of mass you could use this video. Although, for our purposes the center of mass and center of gravity will almost always be the same.


This video gives one specific example of the center of gravity, and it completely changed how I saw it. After you watch the experiment, you will see how all three points of the wooden board meet at one point in the middle (the center of mass).