Explanation :
We know that the gravitational force between two objects is given by :
[tex]F=G\dfrac{m_1m_2}{r^2}[/tex]
where,
G is universal gravitational constant.
[tex]m_1[/tex] and [tex]m_2[/tex] are the masses of two objects.
r is the distance between them
i.e. [tex]F\propto m_1m_2[/tex]
and [tex]F\propto \dfrac{1}{r^2}[/tex]
So, the correct options are :
(1) Moving the balls closer together. The distance decreases and force increases.
(3) Wrapping the soccer ball in layers of duct tape will also increase force because the mass will increase.
(5) Similarly, putting the baseball in a plastic case will increase mass and hence force increases.
