Answer:
B) repel or attract
Explanation:
Gravitational forces and electric forces are very similar in many aspects, however they also have some differences.
Concerning similarities, we can see that their formula is quite similar:
[tex]F_G = G\frac{m_1 m_2}{r^2}\\F_E = k \frac{q_1 q_2}{r^2}[/tex]
where G is the gravitational constant, m1 and m2 the masses of the two objects, r the separation between the two objects, k the Coulomb's constant, q1 and q2 the charges of the two objects. We see that both forces obey an inverse-square law, since they both depend on [tex]1/r^2[/tex].
However, there is one big difference between the two forces. In the formula, m (the mass) can only be positive, while q (the charge) can be either positive or negative. As a result, we have:
- The gravitational force can only have one sign --> in fact, it is always attractive
- The electric force can have 2 different signs --> in fact, it can be both attractive or repulsive (in particular, it is attractive when the charges have opposite signs, and repulsive when the charges have same sign).
