A mass-spring system oscillates so that the position of the mass is described by x = − 10 cos (1.57t), where x is in cm when t is in seconds. Make a plot that has a dot for the position of the mass at t = 0, t = 0.2 s, t = 0.4 s, . . . ,t = 4 s. The time interval between each dot should be 0.2 s. From your plot, tell where the mass is moving fastest and where slowest. How do you know?