At t = 0, a 730 g mass at rest on the end of a horizontal spring (k = 128 N/m) is struck by a hammer, which gives it an initial speed of 2.74 m/s. (a) Determine the period of the motion. s Determine the frequency of the motion. Hz (b) Determine the amplitude. m I have found parts A with no problem...but i was hoping someone could post the formula that I can use to find the amplitude as I am having some real trouble figuing it out.