Question

give reason for the following it is easier to push a letterbox than a similar heavy box on the same floor

Answer 1

If an object has more mass then it has more inertia.
More inertia means the more the object will resist a change in its state of rest.
So a lighter box would be more easier to push than a heavier box in the same floor.

Answer 2

Because the letter box contains letter   while the heavy box contain some heavy objects so we can easily push the letter box compare to the heavy box.