Question

Using Archimedes Principle Fb = ρ * Vdisp * g, explain why a ship that weighs thousands of pounds can float in water, but a solid block of metal having the same weight will rapidly sink in water.

Answer 1

Ans: Any object in water experiences two forces :-

1.) GRAVITY FORCE , which pulls down the object because of its mass.

2.) BUOYANCY FORCE : It's a upthrust, which pushes the object up.  

And when these forces balances, the object floats.

Here, The weight of water displaced by solid block of metal is much less than the weight of the block. So,The buoyancy force of a metal block is much smaller than its gravity force. Therfore, the metal block sinks.

But in case of ship, The weight of water displaced by ship is equal to the weight of the ship itself. And hence, because of its body design, which contains a lot of air, it displaces (pushes aside) enough water so that the buoyancy force is equal to its gravity force. That is why a ship floats.