 So in this video, we're going to do actually some problem-solving with kinetic friction. If you haven't watched the other videos that describe the concept of friction and the specific terms in this equation, you want to go back and watch those. They're in my playlist. In this case, we're going to start some problem-solving. And I'm not writing these out as word problems, but let's just say we're given a problem where you're told that the coefficient of kinetic friction has a particular value, maybe 0.36. And you're given a value for the normal force. And again, I'm just going to make up a value here of maybe 15 Newtons. Remember, again, force is in Newtons, and a coefficient of kinetic friction does not have a unit. So in this case, what we would be solving for is we would be solving for the frictional force. And in this case, we don't have to rearrange this equation. So we can take our equation and simply plug in our values. And the particular values that I'd be plugging in is the 0.36 and the 15 Newtons. And when you plug those into your calculator, you're going to get a value here of 5.4 Newtons. So that tells us that the frictional force is 5.4 Newtons. When I apply a normal force of 15 Newtons between two surfaces where the relative coefficient of kinetic friction is 0.36. So this is one example. Let's say I have a slightly different example. And now I'm maybe doing an experimental setup where I can measure the normal force and I can measure the resulting frictional force. And what I need to solve for is the value of the coefficient of kinetic friction. This is actually how they go through and find particular values for the coefficient of friction. They do it experimentally. In this case, let's use some made-up values again here. Let's say 26.5 Newtons and 3.75 Newtons. Whatever your particular word problem is will give you the knowns that you need. Now to rearrange this equation, I've got to do a little bit of algebra here, dividing through the normal force such that my coefficient of friction is the frictional force divided by the normal force. At that point, I can go ahead and plug in my values and actually put that into my calculator and get a value for the coefficient of kinetic friction of, well, around to get to three significant digits, I would get 0.142. Now, it doesn't have any units because I had both Newtons on the top and Newtons on the bottom, so those canceled and left me with a dimensionless coefficient. One last example showing another algebra rearrangement for this one. Let's take a look at what if my knowns are, I've got a particular value for the friction and I know my kinetic friction coefficient and I'm solving for my normal force. So this would be the next set of algebra. Now, even without giving you guys any numbers here, you should be able to go back, look at this equation up here and figure out how to rearrange to now solve for the normal force. And in that case, we're going to be taking our normal force is equal to the frictional force divided by the coefficient of kinetic friction. So if I plug in actual values here, I'm going to have something which is a Newton value for the frictional force and I'm going to have some sort of probably decimal value with no units since most of our coefficients of kinetic frictions are going to be between 0 and 1, maybe up to 2, but probably between 0 and 1. And when I plug those values in, I'm going to get a normal force in this case of rounding it off again to three significant digits would be 56.3 Newtons. And again, it's Newtons but divided by no units, so it leaves me with Newtons. And almost all the cases we're going to be dealing with unless there's sort of really sticky surfaces, the normal force is going to be larger than the frictional force, so that makes sense.