We know that torque causes rotation, but the question is how much to show you I brought together my three favorite scientists and I've put them on massive disks. So here we have Michael Faraday. Revolutionized classical physics invented the idea of the field yet only had an elementary school education, also a brilliant experimentalist. We also have Marie Curie here who's the only person to win a Nobel Prize in both physics and chemistry, pretty impressive. I'm also a big fan of her distant relative Sherry Curie. And then finally we have Carl Sagan, astronophysicist and who is a big popularizer of science. If you haven't seen the original 1980 Cosmos, I want you to turn off this ridiculous video and go watch it right now. It'll blow your mind. The predictions he made almost 40 years ago, frighteningly accurate. So these are my three scientists and what you don't know about these is very very little known fact about these three scientists is they all had the same mass. It's actually true. If you look up their weight all about the same. So what I've done is I've made these disks all have the same mass. Each disk is about 380 grams. What we're going to do is we're going to apply the same torque to each disk. So each disk has a section of string they're all the same length and they each have a 20 gram weight. So they're all going to feel the same force mg down, 20 grams times gravity. And they're all going to pull at the same radius because they're all the same size. And we'll apply the same torque to several things that are the same mass. See what happens. Here we go. So I'm just going to pull this out of the way and watch them go. So maybe you've got to feel for the relative rotational velocities. So let's see what physics says what happens because we're not breaking new ground here. We really do know what's already going to happen. And the answer is it's going to follow Newton's second law. You could say Newton's second law for rotation. It's sometimes what it's called. It's the basis for rotational kinematics and it looks like this. If you have an object and you say the sum of all the torques are applied equals i alpha. Where this is the moment of inertia we've been talking about and this is the angular acceleration. So this is the basic equation you always go to when you're figuring out a kinematics problem. That's the total torque. I is, I don't know what it called, it's called the moment of inertia. And alpha is angular acceleration. So now we can maybe understand why our disks of the same mass ended up going at different angular accelerations. It's because we know that moments of inertia depends on more than just the mass. It depends on how the mass and how the mass is distributed. So now I'm going to pull them off and show you their mass is in the back. So you can see Faraday had the highest alpha and Curie went down. She rotated a little slower. And then finally the slowest, perhaps the one with the most gravitas will not really is Sagan. So you can see this would be the, even though they all have the same mass, this is the smallest moment because the mass is close to the axis, the smallest radii for most of the mass elements, and then medium and then highest moment. Since they all had the same torque, smallest moment, highest angular acceleration, medium, medium and then biggest moment, smallest angular acceleration.