Two small aluminum spheres, each having mass 0.0250kg, are separated by 80.0cm.

Hi, thank you for posting your question here at .

You have not completed your question. But assuming from the given values,

m1 = m2 = 0.0250 kg
d = 80 cm = 0.8 m

you might be finding the attractive force between the two aluminum spheres. If so, we use the Law of Universal Gravitation:

F = G*m1*m2/d^2, where G = 6.673E-11. Substituting,
F = 6.673E-11*0.0250*0.0250/0.8^2
F = 6.52E-14 N

Independent variable is something that is changed in a experiment. 

The object's initial distance above the groundthe object's initial velocity