Hey guys can you help me with this problem it's giving me a headache. "If 2500 kg roller coaster car begins its descent from 500m above above the first hill. What is its kinetic energy at the bottom of the hill."

Four objects each with charge +2.0×10−7c are located at the corners of a square whose sides are 2.0 m long. part a what quantities can be determined using this information? check all that apply. the electric force on a charged object placed at the center of the square. the mass of each object. the total electric potential energy of the system consisting of the four charged objects. part b find the electric force on a charged object placed at the center of the square.