If the force of gravity acts on all bodies in proportion to their mass why does not a heavier body falls faster than a lighter body?

Answer 1

Because, in non-technical terms, inertia accompanies mass as well as gravity. Along with an increased mutual pull, the bodies have a tendency to remain at rest. The larger the mass, the more energy is required to overcome the inertia. Here is a non-technical way to visualize this and have it make, perhaps, a little more sense. If I am standing on earth in a vacuum (I'll be wearing my handy pressurized suit) and I'm holding a 10 kg mass and a 1 kg mass, I might intuitively guess that the 10 kg mass will fall faster to earth. But let me imagine that I am standing on earth at the exact opposite position on earth, my antipode. I'll assume there is land there. I see myself 'upside down', holding on to the same weights. It's now a little more intuitively clear that while the gravitational 'pull' between the earth and the 10 kg mass is a little stronger, the earth has to pull 'up' on a slightly more massive object. From this position one could playfully imagine that it would be the less massive object that would be pulled 'up' faster. Of course this is not the case, but you can see how a different perspective can alter the way we make inferences about things.

Answer 2

In Newton's theory, Force = Mass*Acceleration (F=ma), so (by switching things around mathematically) Acceleration = Force/Mass. However, the force that a gravitational body exerts on another mass is proportional to the size of that mass, so therefore (at any given distance) Force/Mass will be a constant. In more concrete terms, the force that the Earth exerts on a one ton weight is much greater than the force it exerts on a one ounce weight, but the mass of a one ton weight is much greater as well. These two factors balance out so that everything at the surface of the earth accelerates at the same 9.8 m/s2

Answer 3

This can be understood in several ways, for example:

1) If two separate objects fall at a certain speed (acceleration, actually), it just doesn't make sense that they will fall faster by the mere act of joining them.

2) The object with more mass has more gravitational force on it. To compensate, it also has more inertia. For example, a 2 kg mass, as compared with a 1 kg mass, will have twice as much gravitational force on it; but it will also require twice as much force for the same acceleration (by Newton's Second Law).

(The above assumes there is no air resistance.)