[<< wikibooks] Physics Course/Periodic Motion
== Periodic Motion ==
Periodic motion refers to any motion moving at a distance above and below the equilibrium position and this motion keeps repeat itself over a period of time. This type of motion is also called Oscillation .

== Examples ==
The moving up and down of a spring
The swinging side by side of a pendulum

== Analysis ==

=== The moving up and down of a spring ===
When apply a force on an object of mass m attach to a spring , the spring will move a distance y above and below the equilibrium point
The force acts on the object is

F = m aThe Restoring Force of spring is given by Hook's law as

Fs = - k yWhen The Net Force on the system is 0 then there is no movement

F - Fs = 0
m a = - k y
y =

m
a

k

{\displaystyle {\frac {ma}{k}}}

a = -

k
m

y

{\displaystyle {\frac {k}{m}}y}

v t =

k
m

y

{\displaystyle {\frac {k}{m}}y}

t
=

k
m

y
v

{\displaystyle t={\frac {k}{m}}{\frac {y}{v}}}

=== The swinging side by side of a pendulum ===