1. Net Force: The greater the net force acting on an object, the greater its acceleration. This is directly proportional, meaning if you double the force, you double the acceleration.

2. Mass: The greater the mass of an object, the smaller its acceleration for a given force. This is inversely proportional, meaning if you double the mass, you halve the acceleration.

This relationship is summarized by Newton's Second Law of Motion:

F = ma

Where:

* F is the net force acting on the object

* m is the mass of the object

* a is the acceleration of the object