Introduction (Part - 1) - Oscillations, Physics, Class 11 Video Lecture

hello friends this video on oscillations
part 1 is brought to you by exam feel
calm no more fear from exam the topics
which we'll cover in this lesson our
introduction periodic and oscillatory
motions simple harmonic motion simple
harmonic motion and uniform circular
motion velocity and acceleration in
simple harmonic motion force law for
simple harmonic motion energy in simple
harmonic motion some systems executing
simple harmonic motion damped
oscillations forced oscillations and
resonance so let us introduce the
chapter with what is oscillation there
now in other previous lessons we talked
about several kind of motion for example
rectilinear motion where a particle
moves in a straight line circular motion
where an object moves along a circular
path projectile motion and so on so here
in this lesson we will again study about
a new kind of motion which is often
known as oscillatory motion or
oscillation so before I tell you what is
oscillation the best example that you
can think of as the pendulum of your
clock if you look at your wall clock you
would see the pendulum always moving to
and fro right so that kind of motion is
nothing but oscillatory motion or
oscillation so how we define oscillation
is periodic to and fro motion
as obvious what is periodic any motion
which repeats itself after a regular
interval of time so oscillatory motion
is a periodic motion
it's a periodic to and fro motion would
you invite to and fro that is let us
suppose if this is the initial position
of the particle after a regular interval
of time it comes back to its original
position so that is to and fro so it
goes back and again it comes back to
where it started from
so oscillation is a periodic to and fro
motion let us look at the pendulum of
your clock it is somewhat like this Fred
so what happens in this case if you
observe very carefully this pendulum
ball moves to and fro from its initial
position let us suppose that this is the
position of the ball it is in this
position so it moves to comes back again
crosses this position goes back to this
extreme and and again comes back to
where it started from
so this is basically moving to and fro
and also it is repeating its motion the
same kind of pattern is being repeated
after a regular interval of time so this
is known as oscillation now when you
consider this example you might be
thinking that in our I am in a day to
day life we often call such kind of
motion as vibration we often say that
this object is vibrating if you think
even vibrating vibration is nothing but
a to and fro motion and in vibration as
well the motion is periodic so how do we
differentiate between an oscillation and
a vibration are they both the same or
they are different well there is no
significant difference
between oscillation and vibration
basically both of them are periodic
motion and both of them are 2 &
Promotions but there lies a slightest
difference because of which they both
have been assigned two different names
when the frequency is small we call it
oscillation so what is frequency now
even in your general English frequency
is something it is a quantity which
difference out in what interval a
particular motion is getting repeated
for example if I consider the pendulum
of the clock again here if you observe
the motion of the pendulum it moves
quite slowly to and fro and very logical
so you can very easily observe the to
and fro motion of the pendulum so this
kind of motion can be categorized as
oscillations where the frequency is very
small that is where the same motion or
the same pattern is getting repeated
after the considerable period of time so
you can observe the repetition where
else when the frequency is very high
that is when the to and fro motion
happens very rapidly that you can't even
observe when it goes to the extreme end
when it comes back to its original
position in those kind of situation we
call the motion asked vibratory motion
or vibration for example you can think
of the string of your guitar when you
click a guitar and you move your fingers
over the strings of the guitar what
happens is that the string vibrates so
even in that case this is how the string
vibrates right
so it moves very happily from its
initial position or from its normal
position
along both the ends but the motion is so
fast or so rapid that you cannot observe
very minutely when it goes to the
extreme position when it comes back to
its original position so this is what is
the difference between oscillation and
vibration if the frequency is small it
is oscillation that is the motion
happens
comparatively slowly so that is
oscillation and when any oscillation
with a very high frequency is termed as
vibration just now when to do that
oscillating motion is a periodic motion
so does that mean that all the quotients
which are oscillating will be periodic
or is it something like all periodic
motions which we can see around us will
be oscillating so let us see that every
oscillatory motion which you can think
of is periodic because periodic is a
term that defines oscillatory motion so
it is a necessary condition for a motion
to be oscillatory so every oscillatory
motion will be periodic that means every
oscillatory motion will repeat itself
after a fixed interval of time but every
periodic motion needs not be oscillatory
some of the periodic motions will be
oscillating but not all of them now let
us look at one example of both when you
take the example of the pendulum it is
an oscillatory motion right now since it
is an oscillatory motion so the
definition itself says that it is a
periodic to and fro motion
hence the motion is periodic but when I
talk of any other periodic motion for
example let us think of the motion of
the earth around the Sun so the motion
is periodic right the earth travels
around the Sun in a circular orbit in a
periodic interval of time after the
given interval
it repeats it's fun but is that motion
oscillatory no it is not so it is not
hot as necessary that any period of
motion will be oscillated but vice versa
is always true that is an oscillating a
motion must be periodic now let us take
an overview of the oscillatory motion
there are certain very common terms
which we will keep using as we go ahead
with this lesson now in practice what
happens is oscillating bodies eventually
come to rest as their equilibrium
positions so now let me tell you when I
talk of any oscillating body what do I
mean when I say equilibrium position let
us take the example of your pendulum so
the mass which hangs along this thread
is known as Bob of the pendulum I am
introducing this terminal audience
before the beginning of the chapter so
that value because off and on I will be
using the same terms now when the motion
starts it goes to the extreme position
we call this extreme end as the extreme
position it comes back and again goes to
the extreme other end so this is also
the extreme position now what does
equilibrium position equilibrium
position is that position where the
pendulum tends to go when it tries to
come to rest and if you take the Bob to
one end and just leave it so it will
oscillate from one end to the other for
some time and gradually it will come to
rest so when it comes to rest what do
you think would be the position of the
Bob it would come to the central
position so this position
is known as the mean position or the
equilibrium position of the oscillating
object so which is the oscillating
object here the verb is the oscillating
object it now here you imagine the
scenario as a stone tied to a threat and
it is hanging from some support right
not suppose you take the stone and take
it to one of the extreme corner and then
just leave it so what will happen it
will start oscillating but do you think
that it will keep oscillating infinitely
no after a certain period of time it
will come to rest because of the
frictional forces around so when it
comes to rest do you think it will come
back to the extreme position and stop
there no it's a come back to its mean
position so mean position or equilibrium
position is that position where the
object tends to come to rest on its own
when no external force is applied right
so this is your main position or
equilibrium position these two are the
extreme positions and in this mass which
is tied to a threat is termed as the
ball of the pendulum thank you please
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