00:01
Hi, in this question it is said that there is a block of mass 5 kg that rest on a rough horizontal surface.
00:10
So first we will draw.
00:12
Suppose it's a rough horizontal surface.
00:17
Okay.
00:18
And on that rough horizontal surface there is a block of mass 5 kg.
00:24
So it's a block 5 kg.
00:28
Okay.
00:29
And it is at rest.
00:31
That means static condition and it's a rough horizontal plane or a surface.
00:37
Now see the coefficient of friction of this rough horizontal surface is also given that is 0 .2.
00:45
Clear? now it is said that if a horizontal force 40 newton is applied, okay, in the horizontal direction on this block that is at static at rest, then what will be? the acceleration of the block.
01:04
So for that we have to consider a horizontal force f, that is 40 newton.
01:11
Now by applying the 40 newton force, what will be the acceleration in that block? so now first of all we have to understand the concept.
01:22
So this concept depends on the friction.
01:27
So it is said that previously the block is at which condition the block is at rest at static right that means at horizontal plane the block is fixed at its position the block is not moving the block is not in motion right so now after some time an external horizontal force 40 newton has been applied on 5 kggg right so now we have to first check that by applying 40 newton force, is the block start moving or not? because it will depend on the limiting static frictional force.
02:14
If this if the horizontal force will exit, if this horizontal force will exit the limiting frictional force, right? then only this block will start moving or shift.
02:31
For that, first we have to find out the limiting frictional force.
02:36
So how to find out the limiting static frictional force? limiting static frictional force is equal to the product of the static frictional coefficient that is 0 .2 is given into r.
02:51
See now what is the normal reaction force exerted by this r horizontal plane.
02:58
What is the direction of r? it will be vertically upward direction and what is the direction of weight it will be vertically downward direction that is m g now see there are no other vertical components so at equilibrium r must be equal to m g okay at equilibrium there are no other vertical components so it must be equal to m g okay so f l is equal to mu according to the definition of friction force so mu is given 0 .2 r must be equal to m g so m is 5 and g we have to consider 10 in this question it is mentioned g is 10 meter per second square so 5 into 10 newton so it's coming 10 now see the limiting static frictional force is 10 newton so limiting static frictional force is 10 newton so limiting static frictional force means the maximum static frictional force offered by this rav horizontal plane.
04:08
Okay, so if the horizontal force will exit this limiting static frictional force, then only the block will start moving.
04:19
So we can see that here, 40 newton is much more greater than 10 newton.
04:25
That means the horizontal force is sufficient to move the block, right? so for that it will start moving with its own acceleration that will be a.
04:37
Okay, so a is the acceleration due to the motion...