What can you tell about two objects if one floats and one sinks?

Answer 1

First, buoyancy force must be defined. A force is just a fancy way of saying weight. But, the buoyancy force of an object is an upward acting force on an object in fluid (water in my example) and is equivalent to the weight of the volume of water that the object sitting in the water displaces. So, boats displace a huge volume of water and thus their buoyancy force, which is acting upwards, is very large; so, a boat will float. So, if two objects that displace amounts of water equal to their volume (think 2 blocks of substances) are put into water, and one sinks while the other floats, then the one which sank has a higher density than water and the one which floated has a lower density than water. But, if one object was shaped like a bowl and was floating, then all you can say is that it has a greater buoyancy force than the other object which sank. Note that when an object sinks, it still has a buoyancy force, but this force is not as large as the weight of the object itself, which is acting downwards, overcoming the buoyancy force. This topic gets even more confusing when talking about foams of various geometries, but I hope what I said kind of helps.