Why does a ship float in water while a needle sink in water?

To understand what makes a heavy steel ship float, you have to think of “floating” as the point at which an object stops “sinking”. An object floats on water because it displaces – or takes the place of – the amount of water equal to it’s own weight. The more water the ship displaces the more “boyant”, or floatable, it becomes. A ship (or anything else that floats) sinks into the water until it has displaced its own weight of water, then it will not sink any further. If a ship weighing 100 tons is placed in the water, it will move aside up to, but no more than 100 tons of water. Because a ship is a lot like an empty bowl – relatively thin steel on the outside and nothing but air on the inside – its actual density is less than that of the water it displaces. So, a 100 ton ship will not displace so much water that it goes down into the water below the sides of the boat. This causes the ship to float on the water. This explains why a solid block of steel will sink and a hollow bowl of ...  more

It is all about displacement. The hull of a ship is supported by the pressure exerted against the hull by the water that is being displaced by the ship. The basic shape of the hull of the ship helps with this also.  more

THEY ARE NOT MADE OF THE SAME MATERIAL, MATERIALS FLOAT, NOT WEIGHTS.  more

Density. Anything less dense than water (density = 1) will float on water. Anything more dense than water will sink. It's interesting that when water freezes, it actually becomes less dense. That's why ice floats in water. The most dense liquid is mercury. You can float a brick in a puddle of mercury.  more

Like a bottle of air will float but a bottle of water will sink. The air is lighter and prevents the heavier container material from sinking. Not very technical...  more

The ship is hollow, so it weight is spread over a large area of the water surface. This makes the ship's bow weigh less then the amount of water it displaces, so it floats. The needle is not hollow, so it weighs more then the amount of water it displaces, so it sinks.  more

Look at the surface area that is touching the water in each case. A needle has a long, extremely thin area, whereas a ship has a huge amount. If you were to put a needle on a piece of foil, it would 'float' again because the surface area that is spread across the water is supported more.  more