Apendulum is made up of a small sphere of mass 0.500 kg attached to a string of length 0.750 m. the sphere is swinging back and forth between point a, where the string is at the maximum angle of 35.0∘ to the left of vertical, and point c, where the string is at the maximum angle of 35.0∘ to the right of vertical. the string is vertical when the sphere is at point b. calculate how much work the force of gravity does on the sphere from a to b. express your answer with the appropriate units.