A point on learning. I, personally, don't learn mathematics very fast. It is necessary for me to visit a mathematical concept several times before it really sinks in and stays put. Please, give yourselves sufficient time to learn and understand the presented concepts. Weight and balance are day-to-day concepts and quantifications. Inertia is generally known, but it is rarely quantified as moment of inertia. Patience, the learning will come in due time.