Why does the force of gravity increase as mass increases?

Answer 1

There are 14.7 lbs of gravitational pull per square inch, when you increase the weight if an object, let's says a shoe box that's empty it will fall to the ground rather easily, but put a pair of shoes in that same box and tape it closed. That box will fall harder and faster because of the weight of the shoes in the box. I hope that make sense. The heavier the item the harder and faster it will fall.

Let's say that shoe box weighs 3 lbs. Multiply the 3 lbs. by 14.7 and that should be the speed for the fall, plus or minus a bit for atmospheric pressure.

Answer 2

Mass doesn't change. Mass is the amount of 'stuff' that an object is made of. That doesn't change.

Whether the object is on the earth, on the moon, in orbit, or in outer space, it has the same mass.

When an object is in a gravitational field and not falling, it has weight. The more mass it has, the more it weighs.

Really this is being asked backwards. The mass doesn't increase as weight increases; rather as mass increases, the weight increases. Weight is mass in the presence of a gravitational field. In all technicality a bathroom scale measures your mass not your weight. If a scale says that someone "weighs" 200 pounds it means that their mass is 200 pounds. To find their weight, on Earth, you multiply by 32.174 ft/s/s. So the weight is 6,424.8 Slugs. Since the gravitational force is constant everywhere on Earth's surface, the only way to increase weight is to increase mass.