Today we looked at the moment of inertia of a body. There was a very brief heuristic of how this is defined but for the purposes of this course we can take this as a formula given to us by physicists. (you should know the formula though!) This number tells us how difficult it is to spin a body about an axis - this depends on the mass of the body but also on how the mass of the body is distributed: A nice video which shows how a good teacher might describe this is here. (You will have to copy and paste this link into your browser.) https://www.youtube.com/watch?v=uyU25DdONjo 

We also introduce a problem to motivate the next lecture - on probability distributions