00:01
All right, so what we have here is a free body diagram drawing problem, and then what we're interested in is the free body diagram for the block on top.
00:11
So that is block a.
00:13
That's this one right here.
00:16
So just to get the two obvious forces out of the way, those being gravity as well as the normal force of block b, pushing up on block a.
00:27
So i'm still going to call that n -subscript.
00:31
However we're told that if we pull on the bottom block b block a will move with it so what that means is that there is friction in between the two blocks specifically static friction that is moving this block to the right so that's part a so in part b we're going to do the same thing but because of newton's third law you know forces and reactive forces it will be useful to draw the free by diagram for both blocks just so that we fully understand what's going on.
01:06
Starting off with the block on the bottom.
01:09
So not only is there the weight of block b itself, but there is also the normal force or the weight of block a pushing down on.
01:22
So of course there's going to be block b's own normal force coming from the ground...