Hi guys, basically i have a few questions with regards to Prof Walter Lewin's videos. Firstly, this is the video of him explaining the flywheel concept with energy involved: My question is, why does a flywheel actually spin when the car goes downwards? how does the flywheel actually converts the translational KE to rotational KE? I'm guessing it's because of the relative motion of the air that spins the flywheel to convert it into rotational KE. However, if that is the case, wouldn't it not spin? As the air can push the wheel where it is in contact with half of it, causing both anti clockwise and clockwise moment. Am I right to say this? or have i mistaken how a flywheel works? Can't really imagine why it spins when it goes down as I have never seen one in reality..haha Next: For this vid, starting from 1:10, you can see that the prof is making the spinning flywheel suspended on a string. while this was happening, why is it that he says the flywheel angular momentum which is pointing outwards, chasing the torque of the flywheel (which is perpendicular to the angular momentum direction)? This is known as precession right? In any case, i would like to know how does the direction of the angular momentum affect the motion overall, as i always thought that the direction of L (usually in the z-axis) is there for illustration purposes only since a curved arrow to indicate the rotating motion of a disk is too troublesome... Thanks a lot guys!!!