This is directly related to Newton's Second Law of Motion:
F = m * a
Where:
* F is the force
* m is the mass
* a is the acceleration
If the force (F) is constant, and the mass (m) increases, then the acceleration (a) must decrease to maintain the equality.
Think of it this way:
* Imagine pushing a small cart with a certain force. It will accelerate quickly.
* Now imagine pushing a much heavier cart with the same force. It will accelerate much slower.
This is because the heavier cart has more mass, and therefore requires more force to achieve the same acceleration.
