Question

Two charged particles near each other are released. As they move, the force on each particle increases. Therefore, the particles haveA) the same sign.B) the opposite sign.C) not enough information

Answer 1

ANSWER

B) the opposite sign

EXPLANATION

The force between charged particles is inversely proportional to the square of the distance between particles, from Coulomb's law:

$F=k_e\cdot\frac{q_1\cdot q_2}{r^2}$

If the force increases it can mean two things: either one or both particles are gaining charge - which is not the case of this problem, or the distance between them is decreasing. In this case, the distance must be decreasing for the force to increase. This means that the particles are moving towards each other, they are being attracted by each other. Since only particles with opposite signs attract, the answer is option B, they have opposite sign.