L2 Friction Examples - Friction, Science, Class 8 Video Lecture

hello friends this video on friction
part 2 is brought to you by exam for
calm no more fear from exam now as I
said that friction always opposes
applied force so that means whenever I
mean when I say that friction is always
trying to oppose motion that means if
you talk about a new object let us take
the same example so in this case the
direction of motion is this the ball is
moving in this direction now what is the
direction of applied force if you see
here we are applying a push we are
trying to push the ball in this
direction so this is the direction of
applied force we are applying force in
this direction and where is friction
acting so friction is acting in this
direction so this is the direction of
friction so friction is always opposite
to applied force that is one thing and
friction acts parallel to the contact
surface so if you see here this is the
surface so let us assume that the ball
is rolling on a table and this is the
table so this is the contact surface and
the friction will always act in a
direction parallel to the contact
surface so whenever you have the contact
surface friction will be parallel to
that surface so let me give you a few
more examples to explain so let us
suppose that instead of a horizontal
surface you have a slanting surface like
this let us suppose you have a slope
like this and you have an object here
and this object is sliding in this
direction so it is falling down to slope
so the object is moving in this
direction so what will be the direction
of force of friction so friction will be
in the opposite direction of motion that
means this would be the direction of
friction why this is the direction
because frisch's
one thing is friction will be opposite
to applied force second thing is
friction has to be parallel to contact
surface and this is the contact surface
so when this is your contacts earth is
parallel to the
we'll be this direction and it has to be
opposite to that of the applied force so
this would be the direction of friction
similarly if you are considering a
vertical surface like this so let's do
some wall or something and you have an
object which is sliding down here I mean
let us just assume that it is not a
freefall
so in that case since the object is
moving in this direction so the force of
friction will be in this direction and
the force of friction will be parallel
to the contact surface so here you can
see this is the contact surface so this
is how you can determine the direction
of frictional force so these are the two
points which you have to remember that
it will always be in a direction
opposite to the applied force and
secondly it will always be parallel to
the contact surface so let us quickly
look at few more examples illustrating
the role of friction now as I said just
know that if you consider a person who
is running I mean maybe he could be a
player it could be an athlete he could
be somebody who is just jogging in the
morning so anybody who is running do you
think he or she would prefer a slippery
surface no not really they would prefer
a rough surface because when you have a
rough surface the friction is more
because the surface is rough so the
surface offers more frictional force and
therefore it becomes easier to run on a
rough surface so your a tendency to fall
down on a rough surface is lesser than
the probability of falling down on a
slippery surface so here if you look at
this picture
it depicts a slippery surface now if you
really want to experiment it I would
never ask you to fall down but what you
can try it is may be you just try
walking on the floor at your home so you
will see that you are able to walk
comfortably now what you do is you pour
some water on the floor or pour some oil
on the floor or some powder on the floor
and you will see that the floor tends to
become more slippery and then when you
walk on the same floor you feel like
your feet will sleep and you will fall
down so the chances of slipping
increases when the friction is reduced
so in case of a slippery surface the
friction is less whereas in case of a
rough surface the friction is more and
when friction is more so if your legs
get a better grip and therefore it is
easier to walk or easier to run
similarly when you consider your car now
it is completely under your control what
is under your control the movement of
your car whenever you want you can stop
the car whenever you want you can start
the vibe you can increase the speed you
can decrease the speed so everything is
under your control but in all of these
movements whether you are stopping your
car whether you are starting your car so
everywhere friction is playing a role
because had there been no friction in
that case first of all the car would
have not been moving on the road because
it means the same thing there is no
friction so either if it is moving it
will move forever it will never stop and
if it is at rest it will never start
moving if there is no friction secondly
it is not only the friction which is
there between the tires and the road
surface that is the that is not only
place where friction is playing a role
even when your tires are moving so when
the type wheels are rotating so even
inside there is friction between
different parts of the we so that is
also friction plays a very important
role in machinery because inside the
machine so if you look at the engine of
your car if you get inside try to look
inside the engine you can see that there
are so many small small machinery parts
where there are so many motors which are
running and all these machines are able
to perform their job because of friction
so friction plays a very important role
in our day-to-day
like so like when you look at the
definition of friction it always talks
about opposing motion opposing motion so
people get an impression they look a
friction and something who always tries
to oppose stuffs oppose movements so
friction is not a nice thing but when
you actually look at it friction is
something which is extremely necessary
as well so we will talk about the pros
and cons of friction thank you please
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