Respuesta :
Function of basic harmonic motion is as follows:
[tex]x(t)=A\sin (\omega t+\phi)[/tex]Here,
[tex]A\text{ is amplitude, }\omega\text{ is angular frequency of harmonic motion, }\phi\text{ is initial phase}[/tex]If pendulum starts from position zero, at position zero phase of pendulum is zero.
Hence, function of harmonic motion is as follows:
[tex]x(t)=A\sin (\omega t)[/tex]Function given for this case is,
[tex]x(t)=0.733\text{ sin (3.762t) }\ldots(1)[/tex]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),
[tex]\begin{gathered} x(10)=0.733\sin (3.762\times10) \\ x(10)=0.733\text{ (-0.079)} \\ x(10)=-0.058\text{ m} \end{gathered}[/tex]If starting angle of pendulum is,
[tex]\begin{gathered} \phi=60^o \\ \phi=\frac{\Pi}{3} \end{gathered}[/tex]Step-2:
Hence, Initial function of pendulum is,
[tex]x(t)=0.733\sin (3.762t+\frac{\Pi}{3})\ldots(2a)[/tex]Now, changing the starting angle,
[tex]\text{from 60}^oto30^o[/tex]Function that repersents the position,
[tex]x(t)=0.733\text{ sin (3.726t+}\frac{\Pi}{6}\text{) }\ldots.(2)[/tex]Step-3:
Now, starting angle of pendulum is,
[tex]\phi=60^o[/tex]Length of pendulum is,
[tex]l=0.4\text{ m}[/tex]Period of pendumum is,
[tex]T=2\Pi\sqrt[]{\frac{l}{g}}[/tex]Substitute known values in above equation,
[tex]\begin{gathered} T=2\times3.14\sqrt[]{\frac{0.4}{9.8}} \\ T=1.27\text{ seconds} \end{gathered}[/tex]Angular frequency of pendulum is as follows:
[tex]\begin{gathered} \omega=\frac{2\Pi}{T} \\ \omega=\frac{2\Pi}{1.27\text{ s}} \\ \omega=4.944\text{ rad/s} \end{gathered}[/tex]Now, new function of pendulum is,
[tex]x(t)=0.733\text{ sin (4.944t+}\frac{\Pi}{3}\text{)}[/tex]Step-4:
Now, replacing value of angular frequency,
[tex]\omega=4.5\text{ }[/tex]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:
[tex]\begin{gathered} T=\frac{2\Pi}{\omega} \\ T=\frac{2\times3.14}{4.5\text{ rad/s}} \\ T=1.4\text{ seconds} \end{gathered}[/tex]Formula of number of period compeleted by pendulum is as follows:
[tex]n=\frac{t}{T}[/tex]Number of period compeletd by pendulum in t = 60 seconds,
Substitute known values in above equation,
[tex]\begin{gathered} n=\frac{60\text{ s}}{1.4\text{ s}} \\ n=42.85 \end{gathered}[/tex]42 periods compeleted by pendulum in 60 seconds.