Work must be shown for all questions. This means the following should be included in each of your answers: (A) Chosen formula (s) rearranged to find the missing variable (B) Substitution of values (including the units) into the rearranged formula(s) (C) Final answer with units (and direction, if necessary) to the proper number of significant digits 1. The G Key below middle C on a piano keyboard vibrates with a frequency of 390Hz. Determine the period of vibration. 3 marks. 2. Determine the period of a simple pendulum having a length of 80cm. 3 marks