* Mass of the objects: The more massive the objects, the stronger the gravitational force between them. This means a larger planet will have a stronger gravitational pull than a smaller one.

* Distance between the objects: The closer the objects are, the stronger the gravitational force. This is why you feel a stronger pull towards the Earth when you are standing on its surface than when you are in orbit.

The relationship between these factors is described by Newton's Law of Universal Gravitation:

```

F = G * (m1 * m2) / r^2

```

Where:

* F is the force of gravity

* G is the gravitational constant (a fixed value)

* m1 and m2 are the masses of the two objects

* r is the distance between the centers of the two objects

In summary, the force of gravity is stronger when the objects are more massive and closer together.