Three equal point charges, each with charge 2.00 μC , are placed at the vertices of an equilateral triangle whose sides are of length 0.250 m . What is the electric potential energy U of the system? (Take as zero the potential energy of the three charges when they are infinitely far apart.) U = nothing J

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?