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But you already know about this, because Fg It is what standards call the “weight” of the body, and for a given size, the weight depends only on the density. Now, if you dropped these blocks into a lake, obviously the Styrofoam would float and the steel would sink. Obviously it has to do with density.
What if you had a mass of water of the same volume? If you somehow manage to hold this water cube, it will feel very heavy, around 62.4 lbs. Now, if you carefully placed it in a lake, would it sink or shake on the surface like Styrofoam? No, right? It’s just going to sit there.
Since it is not moving up or down, the total force on the water mass must be zero. This means that there must be a force that opposes gravity by pushing upward with the same force. We call this floatFor any object, the buoyant force is equal to the weight of the water it displaces.
So let’s think about this. The steel mold displaces the same amount of water, so it has the same upward buoyant force as the mass of water. But because it is denser and has more mass, it heads downward.
In general, an object sinks if the force of gravity exceeds the buoyant force, and floats if the buoyant force exceeds the force of gravity. Another way to say this is that an object will sink if it is denser than water and will float if it is less dense.
Right in the middle, the object will neither sink nor rise to the surface, which we call neutral buoyancy. Humans are very close to neutral because our bodies are made up of 60 percent water. That’s why you feel Weightlessness under water, the buoyant force is largely equivalent to the force of gravity.
avast! Hang in there, my friend. Aircraft carriers are made of steel and weigh 100,000 tons, so why would they do that? they Floats? Can you guess? That’s because of its shape. Unlike a block of steel, a ship’s hull is hollow and filled with air, so its volume is large relative to its weight.
But what if you start filling it with goods? The ship becomes heavier, which means it must displace more water to reach this equilibrium point. In general, when you launch a boat or ship into the water, it will sink down until the weight of the water you’re pushing aside equals the total weight of the boat.