Why is it easier to push a heavy block from behing than to press it on the top and push?

STATEMENT-1: It is easier to pull a heavy object than to push it on a level ground and STATEMENT-2: The magnitude of frictional force depends on the nature of the two surfaces in contact.

Why is it easier to swim in a sea than a river ?

Why is it easier to maintain the motion than to state it?

Why is it easier to open a tap with two fingers than with onw finger ?

Why is it easier to charge a ballon on a dry day than on a humid day ?

It is easier to push an empty box than to push the box full of books.Why?

It is easier to pull a lawn roller than to push it because pulling .