 Now, we look at torque and angular acceleration. And we need to review a few things that we've already seen, specifically the equation for torque, the relationship between angular and translational quantities, and the moment of inertia equation. Now, I've got previous videos on each of these three. And you might want to take a look at those just to remind yourself if you're not quite sure. So we'll start with torque. To have a torque, you needed a tangential force that was offset from the axis. And as an equation, that was torque, the Greek symbol tau, the tangential force, and the distance to the axis r, sometimes called the radial distance. Now, because we had a force, we know that force causes acceleration. So my tangential force could be written out as the tangential force equals the mass times the tangential acceleration. So in my torque equation, I can put my MAT, my mass and tangential acceleration, in place of the tangential force. I'm going to look more at this tangential acceleration. We had a relationship between the tangential acceleration and the angular acceleration, such that tangential acceleration was equal to angular acceleration times the radius. Or in this case, the radius is the distance to the axis of rotation. So I can place this into my equation, where now I'm replacing that A of t with alpha r. So now I've got my equation here. And the first thing I'm going to do is rearrange the order of some of these terms. So I haven't changed the equation itself. I've just regrouped everything else out in front with my alpha behind. Now, I've got this quantity here. And from our review, we'll recognize that that is the moment of inertia, where I can use the simple capital I to stand for that MR squared moment of inertia part of the equation. So then I've got a final equation that the torque is equal to the moment of inertia times the angular acceleration. Now, I did this assuming I had just one force, but I could have more than one. I could have more than one torque acting. In that case, I just need to make sure I'm working with the net torque. So if I have the sum of the torques, the sum of the torques net torque gives me an angular acceleration. Just like our sum of the forces caused a linear acceleration. Now, let's take a look at the units for this. Moment of inertia has units of kilogram meter squared. And angular acceleration is radians per second squared. I can put those together to get kilogram meter squared per second squared. Remember, our radian is a placeholder to let us know what kind of angular units we're really supposed to be working with. Now, over here on the left-hand side, my net torque is going to be a Newton meter. And I can simplify this, or rather, expand it out if I remember that my Newton is a kilogram meter per second squared. So I have a kilogram meter per second squared times a meter. I see that these two things are equal to each other. So I have the same units for torque and for the combination of moment of inertia and angular acceleration. So that's the basic connection between torque and angular acceleration.