00:03
In this problem, we have to arrange the situations in increasing order of kinetic friction acting on the block.
00:11
So first of all, we will draw free body diagram for each of the cases.
00:17
So what are the forces that are acting on the block in case of a? so there will be a normal reaction and weight of the block that will act in downward direction and there will be friction force that will act opposite to the sliding direction.
00:32
Now again if we draw free body diagram for the case b so there will be a normal reaction there will be weight of the block and there will be kinetic friction that will act in opposite direction of this sliding tendency now in third case there again there will be normal force normal reaction weight of the block that is m g and friction force so here we will try to find the net forces in horizontal and vertical direction.
01:12
So if we balance the forces in vertical direction in situation in case a, then we can see here that n will be equals to mg.
01:21
Since there is no motion in vertical direction, therefore forces must be balanced.
01:26
Now if we talk about the second case, so this force, let us say this force is making an angle of theta.
01:31
So this force will have a vertical component of f sine theta.
01:37
Now according to newton's second law, what we can write? n plus f sine theta, since both of these forces have same direction, must be equals to mg.
01:48
So from here we can comment that n is equal to mg minus f sine theta...