Answer :
(1)The frequency of oscillating pendulum =The number of oscillations/ Time taken in Seconds
= 40/4 Hz = 10 hz
then...
Time period is the total time taken for making one complete oscillation
so,
Time Period of oscillating pendulum = 1/10 sec=.1 sec
number of oscillations = 40
time taken = 4s
frequency = 40/4 = 10Hz
time period = 1/f = 1/10 = 0.1s
time taken = 4s
frequency = 40/4 = 10Hz
time period = 1/f = 1/10 = 0.1s