Function of basic harmonic motion is as follows:
Here,
If pendulum starts from position zero, at position zero phase of pendulum is zero.
Hence, function of harmonic motion is as follows:
Function given for this case is,
Statements for zeros:
When net force acting on pendulum is zero, pendulum is in its equilibrium condition.
Which means that, at equilibrium position restoring force due to gravity and tession in a cord of pendulum becomes identical.
Now, at time (t = 0), position of pendulum is at (x=0),
Here, x=0 is equilibrium position of pendulum.
Position of pendulum at 10 seconds is as follows:
Substitute values of time in equation-(1),
If starting angle of pendulum is,
Step-2:
Hence, Initial function of pendulum is,
Now, changing the starting angle,
Function that repersents the position,
Step-3:
Now, starting angle of pendulum is,
Length of pendulum is,
Period of pendumum is,
Substitute known values in above equation,
Angular frequency of pendulum is as follows:
Now, new function of pendulum is,
Step-4:
Now, replacing value of angular frequency,
Amplitude of pendulum will not change. Because, amplitude of pendulum does not depends on angular frequency of pendulum.
Period of new harmonic function is as follows:
Formula of period in terms of angular frequency is as follows:
Formula of number of period compeleted by pendulum is as follows:
Number of period compeletd by pendulum in t = 60 seconds,
Substitute known values in above equation,
42 periods compeleted by pendulum in 60 seconds.