00:01
We're told that our guests at a party decide to use this three meter long five kilogram kilogram board as a seesaw using a small bench as a fulcrum.
00:12
An 82 kilogram man sits on one side and a 64 kilogram woman sits on the other side and we want to know where should the bench be located so that the board balances.
00:27
So i've drawn a schematic here.
00:31
We have the weight of one person here, the weight of the other person here.
00:37
We also have the weight of the board itself that acts through the center of mass.
00:42
So if the board is three meters long, then this thing acts at one and a half meters from each end.
00:49
And what we want to figure out is where this fulcrum should be.
00:52
So i've defined x1 as the distance from the fulcrum to the first person and x2 as the distance of the fulcrum.
01:00
From the fulcrum to the second person.
01:04
Now, if we look at balancing our moments, we have that the torque from this person, again we're calling clockwise positive is their weight times the distance from the fulcrum.
01:24
So that's the torque generated by this person...