A woman can row her canoe at 2.5 m/s. If she faces an opposing current of 3.0 m/s, how fast will she go forward?

V = - 0.5 [m/s]

Explanation:

In order to solve this problem, we must use the principle of relative speeds. This is for an observer who is on the edge of the river he can see how the river moves to the left and the woman tries to move to the right but can not since:

That is, the person sees how the woman moves to the left but with avelocity of 0.5 [m/s] to the left

electric field is a function of 1/r^2

yes, the force per unit charge for a point charge is inverse square law.