Friction:A Necessary Evil Video Lecture | Science Class 8

hello friends this video on friction
part 8 is brought to you by exam feel
calm no more fear from exam so now the
question is do you have always seen so
far that friction is always trying to
oppose motion so some people are still
not convinced that friction is something
really useful but yes friction is
absolutely necessary because without
friction we will see that and then a lot
of things cannot happen without friction
so this is where we say that friction is
a necessary evil
that means on one hand it is necessary
and on the other hand it is against us I
mean it is not good for us so we will
look at both the advantages as well as
disadvantages of friction so first let
us talk about why friction why and how
is friction necessary it helps us to
walk
just imagine had there been no friction
at all you are walking on a completely
smooth surface I am given if you spill a
lot of oil on the floor and you feel
that the surface is extremely c3 and you
are not able to walk but even that
smooth surface is not perfectly smooth
because perfectly smooth sand pieces do
not exist
but on slippery surfaces itself you are
not able to walk so how will you walk on
the surface without any friction so it
helps us to walk so many tells us to
walk in definitely helps us to run and
jog and do all kinds of movement it
helps us to who and thinks we are able
to pull the objects because the
instruction there is some force which is
preventing the object to move otherwise
if there is no friction what we have in
here in the picture you see that we are
holding a carrot so the carrot will not
remain with his arm
grip so it will always continue to move
it will not feel like coming to rest
ever stop a moving object has there be
no friction an object which is moving
would have been moving forever it would
have never stopped it helps us to start
or stop a vehicle so if you see the
vehicles the moving vehicles
or vehicles which are at rest they start
moving that also happens because of
friction because you see initially when
you applying force to start to make an
object move which is at rest initially
doesn't move because the force of
friction opposes its motion but after
some time the force of friction doesn't
increases any further and then the
object starts moving so without friction
this all these things will not happen it
helps in grinding so you would have seen
that for cooking when you stop slow
grind spices you grind often you grind
vegtables at all so all these are
possible because of because you have a
mixer grinder in your place and that
makes a grinder if you see that movement
which happens inside the machine that
happens due to friction because if there
is no friction that movement will not
happen helps in construction purposes so
when you talk about liquid constructions
so everything starts from small things
so you want to hammer a name so for that
also you need friction because if there
is no friction the Navy will not get
into the particular object where you
want to hammer it you will not be able
to hammer it at all because everything
will sleep off so you will not be able
to do it so there will be no
construction it helps us to write we are
able to hold the pen or pencil because
of friction and due to friction only we
are able to write like if you see if you
take and a paper which is completely
oily so do you think that you are able
to write on it properly you are able to
write on it because the friction is less
in that case makes matchstick ignition
possible we're able to light a
matchstick you have seen that you take
the mastic and then you just rub it on
the sides of the matchbox and then you
wrap over it friction produces heat and
that heat produces the fire so that's
how we are able to light a matchstick so
all these things might appear to be
small but if you look at it without
friction the machines will stop going on
because inside every
you have lot of movements taking place
and they would have not been possible
without friction so if there is no
friction I mean the existence of living
organisms will also become very much
difficult because when all these things
will going to happen and how will be
existing but at the same time friction
can cause troubles as well let us look
at some of the disadvantages it opposes
motion so that is the first thing it
always tries to stop or it will always
try to prevent the movement of an object
so any object which is trying to move
friction will always try to bring some
obstacles in the motion of the object
friction produces heat and heat results
in wastage of energy what is heat heat
is nothing but a form of energy now I
gave you the best example so heat is a
form of energy so I was telling away
that if you rub your hands together you
rub your hands together for quite some
time and you can feel that your hands
are warm no that's because a lot of heat
was produced what is heat heat is
nothing but a form of energy so due to
friction unnecessarily a lot of heat
energy gets wasted and we do not want to
waste energy in any form because energy
is precious and we are constantly trying
to find out new sources of energy but
here because of friction we are
unnecessarily wasting or losing a lot of
energy in the form of heat wear and tear
of machinery parts as I mentioned before
also if you look at any type of machine
starting from small machines like a
drilling machine or a washing machine or
a big machinery in a factory or industry
so each of these machines they have a
lot of different parts which have been
joined together so the construction of
those machines have been possible
because of friction so the machinery
parts are able to move that is also
because of friction but at the same time
due to those friction a lot of heat gets
produced now due to the loss of energy
or due to this
the machinery parts tend to get damaged
over time so in order to overcome that
frictional force more power needs to be
given to the machines so that they are
able to do their job it is something
like this let us suppose you have your
toy car there is a force of friction
acting in this direction but you want to
make it move in this direction so you
really need to apply a greater force
than the force of friction so that the
car moves in this direction so in a very
similar way these machines they already
have a lot of friction involved within
them because of their movement because
of the construction so when you want
that machine to do a particular job and
you want that machine to have some sort
of movement so you need to apply a power
or you need to give sufficient power so
that it is able to overcome the
frictional force so that means more
power needs to be given to machines that
is also a loss in one way
noise produced in machines a lot of
noise gets produced and that is also due
to friction because when to set this is
in contact with each other they move
with respect to each other a lot of
noise gets produced so there are a lot
of Addie's advantages associated with
friction mostly with regards to machines
and that is why industries and factories
so that is how friction can cause us a
lot of troubles in terms of machineries
being used in industries and factories
and because looking at the advantages
and these advantages associated with
friction it is termed as a necessary
evil that is on one hand it is extremely
necessary because without this again we
cannot do our daily activities we cannot
survive and on the other hand because of
so many disadvantages mostly due to
wastage of energy wastage of heat it is
also termed as an evil so friction is a
necessary evil
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