Discuss the changes in potential energy, kinetic energy, and total energy for a skateboarder going up and down on a half-pipe (u-shaped) ramp. specifically address the energies when the skater is at the highest point (a), half-way down the ramp (b), and at the lowest point (c).

(a) calculate the number of electrons in a small, electrically neutral silver pin that has a mass of 10.0 g. silver has 47 electrons per atom, and its molar mass is 107.87 g/mol. (b) imagine adding electrons to the pin until the negative charge has the very large value 1.00 mc. how many electrons are added for every 109 electrons already present