The roller coaster cars on top of the first hill travel to the top of the second hill and come to a stop. Analyze this motion in terms of kinetic energy and potential energy. State when each form of energy is zero and when it's at its maximum.

If a molecule with a molecular formula of c13h18 is treated with an excess of h2 in the presence of finally divided pt metal under conditions required for maximum hydrogenation of the molecule to give a molecule with a formula c13h24, how many rings are in the molecule?