We will have the following:
2) We can determine that the ratio is constant due to the fact that the acceleration of the gravity on Earth remains constant on the planet. And the mass of the planet is constant.
3) What causes the objects accelerate is the mass of the body that supports them and the mass of the very object. In clasical mechanics the acceleration is due to the influence that a body imparts on another. In relativistic mechanics the acceleration is due to the warping of the space that makes the bodies towards the one with a bigger sphere of influence.
It can also be interpreted as the relationship of the force that is imparted on a body by another and the mass of the smaller object.
