00:01
In this example, we are to estimate the total kinetic energy of the air molecules in a classroom.
00:06
Okay, this room has the dimensions of 4 meters by 10 meters by 3 meters.
00:22
Okay, so it's got a total volume of 120 meters cubed.
00:28
I know the temperature in the room is t equals 24 degrees celsius.
00:37
And i know the pressure in the room.
00:39
Pressure equals 1 atmosphere equals 101 .3 kilopascals.
00:48
Okay, we have air is 20 % oxygen and 80 % nitrogen.
00:59
Okay, so we want to find the total kinetic energy of all of the air molecules in the room, assuming they're 100 % oxygen and nitrogen.
01:12
Okay, and we also have the mass of oxygen.
01:14
Mass of oxygen equals 28 u atomic mass units.
01:24
And nitrogen is, oh no, nitrogen is 28.
01:29
Sorry, mass of nitrogen is 28 atomic mass units.
01:34
Mass of oxygen is 32.
01:38
Okay, now we can model this as an ideal gas.
01:44
I know for an ideal gas, each molecule has a kinetic energy.
01:51
Gke equals n over 2 kbt.
01:57
Okay, kb is boltzmann's constant, and i'll write that down in just a second.
02:02
N is the number of degrees of freedom.
02:08
T is temperature.
02:11
Okay, so for our gas, we have diatomic gases.
02:15
N equals 5...