In automobile hydraulic brakes work on –

Why does an iron nail float on mercury while it sinks in water?

The spray bottles used as window or household cleaner or perfume sprayer work on

What happens when some charge is placed on a soap bubble?

A needle sinks in water whereas a ship made of iron floats on it because :

A piece of ice is floating in a beaker containing water up to its brim. When whole of the ice melts