12. two positive charges, each of magnitude q, are on the y -axis at points y=+a and y=-a where would a third positive charge of the same magnitude be located for the net force on the third charge to be zero? a.) at the origin b.) at y=2a c.) at y=-2a d.) at y= -a

Afisherman notices that his boat is moving up and down periodically without any horizontal motion, owing to waves on the surface of the water. it takes a time of 2.20 s for the boat to travel from its highest point to its lowest, a total distance of 0.670 m . the fisherman sees that the wave crests are spaced a horizontal distance of 5.80 m apart. (a) how much is the wavelength? (b) find the period of the wave. (c) how fast are the waves traveling? (d) what is the amplitude a of each wave?