00:01
We're drawing two free body diagrams.
00:02
So the first one, we're going to be drawing an elevator, suspended by a cable, moving at constant velocity.
00:13
So that's a little hint about the length of our arrows.
00:16
Constant velocity means the net force is equal to zero and that our forces are going to cancel out.
00:22
So what are the forces? so we're always going to have force of gravity there because they are on a planet.
00:27
We have gravity.
00:27
That is the force of gravity is going down.
00:30
And the tension in the cable is going up because we're told it's suspended by a cable.
00:36
So you can either write it as t and some people also write it as force of tension or ft.
00:41
We'll make that a capital t.
00:43
So these are really the same thing depending on what your instructor prefers, but the main part is because net force is zero, these arrows should be the same length.
00:53
Now for b, we want a box slowing down on a flat surface.
00:59
So when it's on a flat surface, our net force in the vertical is equal to zero...