 Why is it that if you take a huge, very heavy wooden box, it floats and if you take a very tiny light spoon, it sinks? Well, that's because we've seen that the things float in water because of the upward force that the water puts or any fluid puts which we call the Boolean force. And it turns out that for the wooden box, the Boolean force is massive. It's bigger than the weight of the box and therefore it floats. And in the case of the spoon, even though its weight is very tiny, the Boolean force is even smaller than the weight and therefore the spoon sinks. But why is that? Why does this have such a huge Boolean force, but the spoon has a much smaller Boolean force? For that we can look at Archimedes principle. Archimedes principle says that the Boolean force equals the weight of the fluid that it displaces. So if I submerge the entire box in the water, then it's going to displace this much fluid and the weight of this displayed fluid is bigger than the weight of the box and therefore the Boolean force is bigger than the weight of the box. Whereas in the case of the spoon, if you look at the weight of the displaced fluid, it's much smaller than the weight of the fluid. And therefore the Boolean force happens to be smaller. But why? Why the weight of the water over here is much bigger than that of the box? But the weight of the spoon over here is smaller than that of the spoon. But why that happens? Why is the weight of this water, this much water, bigger than that of the box? But the weight of this much of water is less than that of the spoon. For that we need to look at the density. So if you look at the density of the wood, it's about 0.5 grams per cm cube, which means that it take one cm cube of wood, it weighs 0.5 grams. But weight of water is 1 gram per cm cube. If you take one cm cube of water, it weighs 1 gram. Therefore, you can clearly see, since every cm cube of water weighs 1 gram, and every cm cube of wood weighs half a gram, clearly this entire shape of water will weigh more than that of the wood. So because wood has smaller density than water, this displaced water will have more weight. And therefore, the buoyant force will be larger. But when it comes to steel, look, steel weighs 8 grams per cm cube. But water weighs only 1 gram per cm cube. So every cm cube of spoon weighs 8 grams, but every cm cube of water weighs only 1 gram. Therefore, clearly this will weigh less than that of the spoon. And therefore, the buoyant force becomes smaller. So long story short, what is the condition for floating? Well, the condition for floating is that you need your object to have smaller density than the fluid. If the density of the object is smaller than the fluid, the buoyant force will be large enough and will float. If the density of the object is larger than the fluid, then it will sink, like in the case of the spoon. So what matters is really the density, as long as the density is smaller than the fluid, then the object will float. So if you ever want to think about calculating whether something's going to float or sink, find out what the density of the object is and how do you find the density? You do mass divide by volume. Find the density and then compare it with the density of the fluid and then you can figure out whether it floats or sinks.