According to Newton's laws of physics, gravity depends on mass and distance. How strong gravity is depends on the attractive force between two objects.
Mathematically, Newton expressed his law of gravity as F=GMm/r^2. In this equation, F is force, G is the gravitational constant 6.67 x 10-8, M and m are the masses of the two bodies and r is the distance between the two objects. According to this, doubling Earth's mass would make its gravitational pull twice as strong. In addition, pulling the object four times the distance away from Earth would make it 12 times weaker.
The object's shape, density and the material it is made from do not influence gravity. In addition to Newton's law of gravity, there are three other laws of motion:
The first rule states that objects that are moving continue at the same speed in a straight line, and objects that are inert stay inert.
The second rule states that when an object changes its movements, those changes are directly proportional to the forces that act on it. Expressed as an equation, this is F=ma, with F being the force, m being the motion and a being the acceleration.
The third rule states that every force that exists has an opposite force. For example, when a person jumps from the ground, he or she is able to do so because the ground is pressing against the force.