Here's why:

* Gravity's Constant Pull: Gravity exerts the same force on all objects, regardless of their mass. This means a 10 kg ball and a 100 kg ball will accelerate downwards at the same rate due to gravity.

* Neglecting Air Resistance: In a perfect vacuum, with no air resistance, both balls would fall at the same speed and reach the ground simultaneously.

Important Note: In reality, air resistance can play a role. A larger, heavier object might experience slightly less air resistance than a smaller, lighter object, meaning it might fall slightly faster. However, the difference in this case would be minimal.