Buoyancy What Makes Something Float or Sink

kids want to know have you ever taken bath or played in swimming pool lake Roshan maybe you've noticed that there are some things that make really good bath or pool toys and other things well not so much the term buoyancy refers to how well something floats or sinks if something is able to float we would say that it's buoyant so what makes something float or sink generally we can determine if something can float by feeling its weight usually if something is light it floats or is positively buoyant if it's heavy then it sinks or is negatively buoyant this is an easy enough explanation for us to accept right but the idea becomes shaky when we consider why something really really heavy like cruise ship is able to float to understand this we need to understand the concept of density density is amount of stuff or mass something has inside of it compared to its volume or size for example if we look at this bucket full of sand we would say that it's more dense than this identical empty bucket because the bucket full of sand has more stuff it's got more mass another example is this bowling ball it has more mass than basketball because if basketball is full of air but bowling ball is full of stuff so even though the bowling ball is smaller it's more dense than the basketball so what does this have to do with buoyancy the next concept we need to tackle is called Archimedes principle our Khomeini's was mathematician and philosopher who lived in ancient Greece he had been stumped on problem he was trying to figure out for the king so he decided to take bath when he was sitting in the bath he noticed that the water level rose when he went into the bath let's pretend that this block is our committee's see how the water level goes up when the block goes into the water this means that in order to make space for his body in the bath the water had to get pushed around in the bath making the water level rise the story goes that he was so excited by this discovery that he jumped out of the bath and ran naked down the street to his laboratory shouting Eureka which means I've got it basically what Archimedes is principle helps us to understand is that if an object is heavier than the amount of water that it's displaced or is something very dense the object will sink like the bowling ball and if the object is lighter than the amount of water it is displaced or something not very dense the object will float like the basketball so back to our cruise ship problem even though cruise ship is very heavy it's also very very large most of the ship is also hollow so it's not as dense as you might think because of this just like the basketball the ship is actually lighter than the water it's displaced causing it to float did you know submarines drive by allowing water to fill part of the submarines called ballasts the air gets vented out until the density of the sub is enough to make it sink ships also use ballasts for balance without them they have tendency to tip in windy weather thanks for watching and don't forget to subscribe