00:01
So the weight of the pillar, i'm going to say wsap, there's going to be mass times the gravity.
00:13
But we're not giving it a mass.
00:15
We know that density.
00:18
There's mass over volume.
00:20
That gives mass to the density time volume.
00:23
Okay.
00:24
So the weight of the pillar can also be written as row, time volume, sorry, times gravity.
00:32
Gravity.
00:34
So the volume of the pillar here, so the pillar is cylindrical.
00:38
So the volume is the cross -sectional area which is par square times the height.
00:45
Okay? so that's what we're going to use.
00:49
So what we're going to have here is the density times your pi r squared, h times gravity.
01:02
So we can do our substitution now...