To increase the gravitational force between two objects, you should decrease the distance between the two objects.
According to Newton's law of universal gravitation, the gravitational force (F) between two objects is given by the formula:
\[ F = G \frac{m_1 m_2}{r^2} \]
Where:
- \( F \) is the gravitational force,
- \( G \) is the gravitational constant,
- \( m_1 \) and \( m_2 \) are the masses of the two objects, and
- \( r \) is the distance between the centers of the two objects.
From the formula, you can see that the force is inversely proportional to the square of the distance (\( r^2 \)). Therefore, decreasing the distance \( r \) results in an increase in the gravitational force \( F \).
On the other hand:
- Decreasing the mass of either or both objects will decrease the gravitational force.
- Increasing the distance will also decrease the force.
So the correct action to increase gravitational force is to decrease the distance between the two objects.