The two vectors 3 and 7 added together

If two metal balls each have a charge of -10^-6 c and the repulsive force between them is 1 n, how far apart are they? (coulomb's constant is k = 9.0x 10^9 n-m^2/c^2? 9.5 m 9.0 mm 9.5 cm 0.9 m .

Why does gravity have a lesser than grater effect on higher altitudes?

Afisherman notices that his boat is moving up and down periodically, owing to waves on the surface of the water. it takes a time of 2.70 s for the boat to travel from its highest point to its lowest, a total distance of 0.700 m. the fisherman sees that the wave crests are spaced a horizontal distance of 6.50 m apart. a. how fast are the waves traveling? b. what is the amplitude a of each wave?