00:01
Small box is held in place against a rough vertical wall by someone pushing on it with a force directed upward at 28 degrees.
00:08
So this is where we have a wall and this is where a block is and the force is directed upward at 28 degrees above the horizontal.
00:21
It means that the force is like this.
00:27
Okay, the coefficient of kinetic and the static friction are given as 0 .4 and 0 .3 and the block slides down unless the applied force has a magnitude of 23 newton.
00:35
So 23 newton, we can say, is the verge of motion.
00:38
It means the block just begins to slide down.
00:41
That's a limiting case.
00:42
So definitely when it starts to slide down, but it's not actually sliding down, static friction, maximum static friction is going to act on it, right? and remember, there will also be a normal reaction which is acting on the floor, which is acting on the block because of the wall, that is fn.
01:00
And then we make the components of 23 as well...