Why does a ship made of iron float while a piece of iron of same mass sink in water?

It’s because an iron ship is not completely solid. It has full of air filled in it. So the average density of the ship as a whole is less than the density of water. Therefore immersed portion of the ship displaces water equal to its weight. So the ship floats whereas a sheet of iron is compact and there are no air spaces inside it. Iron is denser than that of water. The weight of the sheet is greater than the weight of the water displaced by the sheet. So it sinks.

What comes out of a black hole?

In the below figure, All the other parts are just changed its place not in size. how the hole is come?

Which pole is colder, the North or the South?

Both Polar Regions of the earth are cold, primarily because they receive far less solar radiation than the tropics and mid-latitudes do. At either pole the sun never rises more than 23.5 degrees above the horizon and both locations experience six months of continuous darkness. Moreover, most of the sunlight that does shine on the Polar Regions is reflected by the bright white surface.

The South Pole the average temperature is about 56 degrees below zero degrees Fahrenheit (−49 degrees Celsius). At the North Pole the average temperature is a relatively balmy 20 degrees below zero (−29 degrees Celsius).

Why is the Ocean Salty?

All water, even rain water, contains dissolved chemicals which scientists call "salts." But not all water tastes salty. Salt doesn't evaporate when water evaporates. The rain flows back down to the sea, adding a little bit of salt to it constantly. Over millions of years, this makes the sea salty.