The reason the balls fall to the ground is gravity. The gravitational field strength of different planets is not the same. On Earth it is 10 N/kg. What happens when we drop two equal masses from the same height?
You see. They hit the ground at the same time.
But what will happen if we drop two objects with a different mass. Will they behave the same or differently? Will the heavier one drop more quickly? Let's have a look.
The larger ball is heavier. Which do you think will hit the ground first?
They both touched the ground at the same time.
Now we will drop two objects with different shapes.
They got to the ground at the same time.
I'll try these two empty bottles.
Again, they reached the ground at the same time.
What happens if one bottle is full of water? The full one is heavy and the empty one is light. Watch what happens.
They hit the ground at the same time. It doesn't matter if the objects are big or small, of equal or different masses, they will behave the same way. The force of gravity is the same everywhere.