L7 : Compare Sliding & Static friction - Friction, Science, Class 8 Video Lecture

hello friends this video on friction
part 7 is brought to you by exam feel
calm no more fear from exam now if you
compare sliding friction with that of
static friction you will see that
sliding friction always is smaller than
that of static friction now the question
is why so by now we all know what a
static friction the force of friction
which acts on a body as long as it is
not moving as soon as it starts moving
then sliding friction comes into picture
now why is it that static friction is
always more than that of sliding
friction let us try to understand things
now what happens is when an object is at
rest so when your toy car is at rest and
you are trying to make it move so
initially you actually need to give a
greater amount of force in order to
initiate the movement because right now
this the car is at rest it is not moving
at all so if you just give a very small
amount of force you just touch the car
and leave do you think it will start
moving it will not you actually need to
give some good amount of force to make
it move so to start the movement it is
more difficult but once you have given
that adequate amount of force and it
starts moving to retain its movement is
easier because the car is already moving
so even if you just touch it slightly it
will continue to move for some more time
but initiation of the movement is more
difficult now why does that happen
that's because when the object is at
rest in this case so initially the
object is at rest and when this object
is at rest the Interlochen so if you
look at the contact surfaces this is the
contact surfaces and the interlocking
between the surfaces is extremely high
because the object is just sitting there
so the surface of the car and the
surface of the floor they are like well
interlocked so when they have well
interlocked so that time the friction is
also more so when the object is at rest
the interlocking is more and when
interlocking is go then
action is also more and since the object
is at rest which kind of friction is
this this is nothing but static friction
right now what happens you give adequate
amount of force to overcome static
friction and the car starts moving now
when it is moving then what is happening
actually let us have a closer look at
what is happening when it is moving so
this is the surface of contact this is
where the car is in contact with the
floor now as it moves this is how it
happens so it is actually moving in this
direction now forget about the rolling
part as of now that because the wheel is
also rolling so forget about that now
even when it's moving to so it's like
the wheel is first in contact with this
surface then it is contact with this
surface then it is in contact with this
part this part and so on so during
sliding the contact points do not get
enough time to interlock properly so
proper interlock cannot take place
because it is not spending a lot of time
at a particular position it is changing
its position because it is moving so the
interlocking is not happening properly
so when it is moving or when it is
sliding in that case the extent of
interlocking is less not proper
interlocking is able to take place and
therefore in less interlocking would
mean less friction now when the car is
moving the type of friction that is
involved is sliding friction or kinetic
friction which will already notice f
king so that is the reason but that that
kinetic friction or sliding friction is
always lesser than static friction that
is due to insufficient interlocking
during movement now lesson interlocking
would mean lesser friction so I hope the
concept of friction is clear to you the
concept of interlocking should be clear
if you are clear with that you will be
able to understand what is static
friction and water sliding friction in
fact now I will also introduce you to
rolling friction thank you please visit
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