how does a big ship float n a brick will sink ??

Question

can somebody help me explain to my wife why a ship wieghing 250 tons will float and yet a brick wieghing only a few pounds will sink. i know its down to displacent but can't explain properly

Answer 1

Basically an object will displace its size in water. water is dense at about 8 pounds per gallon. a brick is more dense and will sink. a ship is made out of materials that are more dense. but because it isn't solid, ie. there is air in the hull. the amount of water it displaces is more than the ships weight. Looking at a canoe will help you figure that one out.

Answer 2

It's all about Archimedes and him jumping out of the bath and shouting Eureka!

Seriously, the brick is small and solid. The weight of the water in the space taken up by the water that it displaces is less than the weight of the brick taking up that space so it drops to the bottom.
Forget the ship, just imagine a HUGE brick but one that is hollow with only a thin wall of brick and a lot of air inside it. When you put that in the water, the weight of the water that it displaces is less than thin wall of brick +all the air inside it so it will float.
Or think of balloons. You know that an ordinary balloon will float. Now imagine a balloon with a thin skin of heavy metal. As long as the metal balloon is big enough, then the amount of air inside it will mean that the amount of metal sinking into the water + the amount of air contained in it will still average out as less than the weight of the water that it is displacing.

I expect that a physicist will answer this far better than I have, but then I haven't thought about since I was at school and that is a LONG time ago.

Answer 3

I agree with most of the answers, the best part is if you were to take a brick, mold it into the rough shape of a boat with the "skin" of the boat being only as thick as around 3/8 of an inch and spread it out larger than the original size of the brick, it would float too. It's a question of making the "displacement" ( how much water it displaces from under the entire vessel) large enough to support it's own weight. Shape is the key. In other words solid, brick shaped object would sink because it doesn't displace enough area of the water to float. But, if you took the same material, shaped it like I described above, and made it larger, it would displace enough area to become lighter than water and float. I have seen boats made of steel, concrete, wood, fiberglass and animal skins.

Answer 4

if you don't want to deal with the concept of buoyancy, try this.....

if something is denser than water...like a brick...it sinks.

Something less dense, like styrofoam, it floats.

When you are figuring the density of a ship you figure not only the steel but all the air inside the ship as well......that averages out ( some heavy steel and lots of really lightweight air ) to less than the density off water so the ship floats.

Replace the air with water and she sinks.

Answer 5

fill the bath tub up. and take a small rock that is less than a pound and put it in the water so she can see it sinks. Now take out the rock and place it in a square tupperware pan that is about the size of a small cake pan. Place the pan with rock inside into the tub and it will float. you can use this as a visual aid to explain why the amount of suface area that is dispaced causes the rock to now float. Sometimes seeing males it easier for others to comprehend what is being explained

Answer 6

Ok lets break this down. The density of water is about 1000kg per cubic meter. Anything with a density more than that will sink in water.
The density of anything can be calculated by dividing the volume of that object by the mass (you can use weight in the non scientific world). Knowing this, the density of the 250 ton ship is less than that of the water and the density of the brick is more than the water.

I hope this helped. Hit me back if you have more questions.

Answer 7

big ship float brick sink

Answer 8

The word is 'watertight' (sealed against leaking).. a brick isn't!! If you put the same said brick in a watertight container it wouldn't sink and would act as ballast to keep the container on an even keel. The more bricks you put into this container...the more displacement into the water would be used.

Answer 9

Image the brick is made of rubber, squeeze it down to a thumb size cube it would sink and stretching it out to football size field it would float.

Answer 10

A body floats into water when it displaces a volume of liquid whose weight is equal to the submerged part. If the body weights more than the displaced volume it sinks.