00:01
Okay, so this is the free body diagram for the spoo.
00:06
Okay, so there's force p perpendicular to the surface point upward.
00:11
And there's a gravity with the w here, and there should be normal force at point a and b, which is n -a and b.
00:18
And since there's a normal force, there should be a friction as well, which is f -a and fb.
00:23
In this case, f -a and fb are kinetic friction since the spools start moving.
00:28
Okay.
00:29
So therefore along the x direction, we have force fx is equal to f a minus nb, which is equal zero.
00:38
So we have f a is equal to nb.
00:40
And f y, we have p plus n a plus fb minus w equal to zero.
00:45
So w, which is the gravity, is equal to p plus n a plus fb.
00:48
So when the f a can be equal to mu kna, which is equal to nb.
00:52
So therefore fb is equal to mb.
00:56
So therefore have fb is equal to mu k and b...