Period & Frequency - Oscillations Video Lecture - Class 11

hello friends this video on oscillations
part 2 is brought to you by example.com
no hole here from exam please make sure
that you have watched part 1 before
going ahead with part 2 now that I have
given you an overview of what this
oscillatory motion now at least you have
an idea that which motion is referred to
as oscillation so now we will gradually
go into detail of the same so we will
start introducing the features or
parameters which define an oscillatory
motion one by one so we will start with
period and frequency what do we mean by
period of oscillation or frequency of an
oscillation so let us have a look at
that now I will explain all the concepts
or details about oscillatory motions I
will use I've been taking the example of
your simple pendulum simple pendulum
here would mean a stone or a mask time
to a threat so I take this as a
universal example as I go through the
lesson so what's its period P it is the
time it takes for an oscillating
particle to complete one cycle of
oscillation so what do I mean by one
cycle of oscillation how do i define one
cycle of oscillation I told you some
time back that oscillatory motion is a
periodic to and fro motion that means it
repeats a particular pattern so that
that particular pattern which is getting
repeated on and off so that particular
pattern is one cycle of oscillation so
the number of times it gets repeated is
that many cycles of oscillations the
particle is undergoing for example here
in this pentagram if you see this is its
motion so that means here you saw that
started from here if you observe it
again this is where the motion is
starting from it went to the extreme end
it came back to the original position so
that means going and coming back so this
is your one second after this the same
motion is getting repeated right so this
was your one cycle of oscillation so the
time it took for this object to move
from let us say this is point A to point
B and then coming back from point B to
point a so this total line is known as
period of a oscillation
generally it is denoted by capital T it
is often known as the time period of the
pendulum or time period of the
oscillating particle SI unit is same as
the SI unit of time that is seconds now
let us see what is frequency frequency
is nothing but the number of cycles per
second that means how many cycles are
executed or how many times the
oscillating particle is repeating the
same pattern that means here just now I
told you that this is one cycle going
from point A to point B and coming back
from B to a so this was one cycle so how
many such cycles the particle is
undergoing in one second so that is
known as frequency so frequency is
generally denoted by nu the SI unit is
second inverse as it is defined by X as
is as can be seen from its definition
that is the number of cycles per second
so the SI unit has to be second inverse
there is also a special unit which is
often used for frequency that is Hertz
so now let us see how this period and
frequency related to each other the
frequency that is nu is nothing but 1 by
capital T that is it is inverse of the
time period why is it so that's because
what was time period just now I told you
the time period is the time taken to
come in one cycle of oscillation and
what is frequency frequency is number of
cycles per second so what how what is
the number of cycles it what when when
you define time period it is one so you
can say it is one cycle per time period
so that is what is your frequency we can
now talk about displacement till so so
far we talked about period of an
oscillation and frequency of an
oscillation now in the same what is
display displacement when we talk of
talk of oscillatory motion we have
already spoken about displacement when
we were dealing with chapters like
motion in a straight line in motion in a
plane and all those things so they will
saw that displacement was nothing but it
just showed how an object is changing
its position right so that was nothing
but the shortest distance from the
initial position to the final position
now displacement is not always used in
context of position you will see here
that how we use a displacement or how do
we define displacement in case of an
oscillatory motion in an oscillatory
motion we say that the angle from the
vertical as a function of time angle
from the vertical as a function of time
is regarded as a displacement variable
what exactly do we mean by this there to
become clear as soon as I show you your
simple pendulum as I told it is not used
in the context of position alone now if
you see your simple pendulum
what is your vertical
this is your vertical I'm sorry it is
not a turn a straight line but please
cooperate let's suppose this is your
vertical now in this simple pendulum
moves away from its vertical this angle
keeps changing so this angle is nothing
but a an indication of the displacement
so this angle from the vertical as a
function of time that means how is this
angle changing with time because if you
think it in the other way this place can
always talked about the position I mean
how the position is changing right from
which initial position to which final
position the object traversed so even in
this case since the object is not moving
linearly so the parameter that specifies
displacement is the angle because the
object is basically changing its angle
with respect to the vertical so that
angle from the vertical as a function of
time is is what that denotes the
displacement of a oscillating motion now
how do we represent displacement
mathematically and all those things also
maybe keep stirring as we go ahead thank
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