A girl attempts to swim directly across a stream 15meters wide. When she reaches the other side, she is15 meters downstream. The magnitude of herdisplacement is closest to

a)  F = 2.25 10³ N, b) REPULSIVE.

Explanation:

a) The electric force is given by coulomb's law

           F = k q1q2 / r2

in this case nso indicate that the two charges have the same value

           q₁ = q₂ = 2.5 10⁻⁶ C

Let's reduce the magnitudes to the SI system

           r = 0.5 cm (1m / 100cm) = 5 10⁻³ m

let's calculate

           F =

           F = 2.25 10³ N

b) In electricity, electric charges of the same sign repel and those of the opposite sign attract

In this exercise, the balls are equal and are rubbed with the same material, for which it acquires charges of the same type, consequently, as the charges are of the same type, they indicate that the negative force is REPULSIVE.