Which sentence from paragraph 4 most precisely explains the factors that determine the force of gravity?
1. "Newton went much further than this
qualitative description and wrote down
equations that quantitatively describe the
strength of the gravitational force between two
objects."
2. "In words, these equations state that the
gravitational force between two bodies is
proportional to the product of their masses and
inversely proportional to the square of the
distance between them."
3. "This 'law of gravity can be used to predict the
motion of planets and comets around the sun,
the moon about the earth, and rockets heading
off for planetary explorations, as well as more
earthbound applications such as baseballs
flying through the air and divers spiraling
poolward from springboards."
4. "The agreement between the predictions and
the actual observed motion of such objects is
spectacular."