Looking for help with this statics question

Why should seat belts not be mandatory quick plz

Mechanical energy is when the amount of kinetic and potential energies added together remains the same. conserved created lost

Complete these sentences. if a roller coaster train has a potential energy of 1,500 j and a kinetic energy of 500 j as it starts to travel downhill, its total energy isj. once the roller coaster train gets closer to the bottom of the hill, its kinetic energy increases to 1,100 j, and its potential energy decreases to j. when the train reaches the bottom of the track and is traveling along the ground, its kinetic energy isj.