The wetted perimeter comes from the cross section of a channel. Determine the wetted perimeter in a rectangle with help from an applied physics professional in this free video clip.

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The wetted perimeter comes from the cross section of a channel. Determine the wetted perimeter in a rectangle with help from an applied physics professional in this free video clip.

Part of the Video Series: Such Great Physics

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Hello, my name is Walter Unglaub, and this is "how to determine the wetted perimeter in a rectangle." The wetted perimeter comes from the cross section of a channel. So, here, I have a side view, a cutaway view, of a channel which might carry water through it. So, here, the water would be either coming at the screen or away from the screen, and if you take a cross section of the channel, in this case, the cross section, would represent a rectangle, where the top side of the rectangle is the surface of the water. By definition, the wetted perimeter is the total length of the sides of your channel that is in contact with the fluid. So, we can define that mathematically as capital P, for the perimeter, is equal to the sum of sides, from one to N, where capital N is the total number of sides in contact with the water, of the length of each of those sides. So, in this case, if I consider the fact that the cross section of this channel is a rectangle, then I would have some height, H, a length, B, for the base of the channel, and since we're assuming symmetry, because this is a rectangle, I have another height, H. So, we see that there are three sides that are in contact with the water. Therefore, the wetted perimeter of this rectangle would be H plus B plus H, or simply B plus 2H. If we assume that the base is equal to five meters, and the height of the water is one meter, then we see that the wetted perimeter, in this case, would be five plus two times one, which is just two. So, five plus two is simply equal to seven meters. My name is Walter Unglaub, and this is "how to determine the wetted perimeter in a rectangle."