A pendulum is timed as it swings back and forth. The clock is started when the bob is at  the left end of its swing. When the bob returns to the left end for the 90th return, the clock reads 60.0s.

(a) What is the period of vibration?

(b) What is the frequency of vibration?



How long must a simple pendulum be if it is to make exactly one swing per second? (One complete vibration takes exactly 2.0 s)



What is the period of a simple pendulum 80 cm long
(a) on earth
(b) when it is in a freely falling elevator?