]shows the potential energy of a 500 g particle as it moves along the x-axis. suppose the particle's mechanical energy is 12 j. a. where are the particle's turning points? b. what is the particle's speed when it is at x = 6.0 m? c. what is the particle's maximum speed? at what position or positions does this occur? d. write a description of the motion of the particle as it moves from the left turning point to the right turning point. e. suppose the particle's energy is lowered to 4.0 j. describe the possible motions.