 When you submerge an object in a liquid, like say when you go into a swimming pool, you feel a little lighter. Why? Not because your weight decreases, but the water or any fluid pushes up on you. This is called the buoyant force. And it turns out that that buoyant force equals the weight of the fluid that you displays when you're submerging in. And this principle is what we call the Archimedes principle. But what does that mean? Well, see, when you're submerged over here, this much space was even initially filled, occupied by the liquid, right? But now you have occupied it. Your bottom half and your legs have occupied it. Therefore, that fluid now has gone away from that particular place and gone somewhere else. It would have gone somewhere over here. And so that amount of fluid is what we call the displaced fluid. And the weight of that displaced fluid that exactly equals the buoyant force. That's what Archimedes principle says. Now to make sense of this, what would happen if you were to submerge even more? Well, if you were to submerge even more, look, you will displace even more fluid. The weight of the displaced fluid would increase, the buoyant force will increase, and you will feel even lighter. And again, that's exactly what you feel. Like the more you submerge yourself inside a swimming pool, the more lighter you feel. And eventually, what if you submerge yourself completely? Well, now you have displaced the maximum amount of fluid. And so you would have the maximum buoyant force. If you submerge even more, well, you're not gonna displace any more fluid. You're already displacing the maximum amount of fluid. So you now have the maximum buoyant force. But let's see how to actually calculate it. Let's take an example. So let's say that your body volume is, I don't know, maybe about 0.05 meter cube. That's the volume of your body, okay? And we probably already know the density of the water. The density of the water is 1,000 kilogram per meter cube, which means a meter cube of water weighs 1,000 kilograms. With just this data, can we calculate the buoyant force? Well, let's see. Let's see if we can calculate that. So what would be the buoyant force? So the buoyant force, or some people like to call it a buoyant force, what do we wanna call that? So buoyant force equals the weight of the fluid displaced. Weight is just mg. I know g, but what is m? m is the mass of that fluid displaced, mass of this much amount of water. Now, how do I figure that out? How do I know what is the mass of this much amount of water? Well, I know density, density is given to me. So density is mass by volume. Therefore, mass is density times volume. And so I can say that the buoyant force equals the density of the water times the volume of this much water, because that's what we're interested in. So volume of the displaced, volume of the displaced water times g. What would that be? I know the density. That's about, that's 1000 kilogram per meter cube. What is the volume of the displaced water? Well, the volume of the displaced water is the volume of this body, because the entire body is submerged. So the volume of the displaced water is 0.05 meter cube. And notice, this is only true because the entire body is submerged. For example, in this case, notice the entire body is not submerged. So over here, the volume of the displaced fluid is less than 0.05. It's not equal to 0.05. Makes sense, right? Because your entire body is not submerged, entire volume is not displaced, is less than that. But since the whole thing is submerged, it is actually equal to that, times 9.8 meters per second squared. And we can simplify this. If I multiply 1000 times 0.05, I get 50 times 9.8. And that gives me 490. And the units of force would be newtons. And there we go. That is the Boolean force acting on this. And how do we calculate it? By using Archimedes principle.