This is based on Newton's Second Law of Motion:
F = m * a
Where:
* F is the force acting on the object
* m is the mass of the object
* a is the acceleration of the object
If the force (F) stays the same, and the mass (m) doubles, the acceleration (a) must be halved to maintain the equality.
In other words, a more massive object needs a larger force to achieve the same acceleration as a less massive object.
