Fossil fuels currently account for the majority of the world’s energy use because they are a. nonpolluting. b. distributed evenly throughout the world. c. renewable energy resources. d. relatively inexpensive and readily available. the gravitational potential energy of an object is always measured relative to the a. position of maximum mechanical energy. b. surface of earth. c. reference level from which the height is measured. d. location where the object’s kinetic energy is zero. a 12-kg sled is moving at a speed of 2.0 m/s. at which of the following speeds will the sled have twice as much kinetic energy? a. 2.8 m/s b. 4.2 m/s c. 6 m/s d. none of the above the total potential and kinetic energy of all the microscopic particles in an object make up its a. chemical energy. b. nuclear energy. c. e