00:01
In this problem we have a rotating disk which has a moment of inertia of one half mass radius squared.
00:08
We're told the mass of this disk is 15 grams.
00:12
We're going to divide this by 1000 to put it into kilograms which is the correct units and you get 0 .015 kilograms.
00:20
We're told the radius is 2 .2 centimeters and we're going to divide this by 100 to get it into meters which is 0 .022 meters.
00:31
We're told it is initially at rest and it speeds up to a speed of 290 radians per second counterclockwise which means in the positive direction and this happens within a time of 1 .3 seconds.
00:48
We're told that there are two forces f1 and f2.
00:51
F1 has a magnitude of 0 .0984 newtons and since we don't have the diagram we're going to have to put this one as the positive direction and the other one will come out to the opposite direction or this positive if they're both on the same side.
01:08
F2 is the one that we're looking for.
01:11
If we're looking for a force of something rotating chances are you're going to be looking for one of our torque equations.
01:18
What torque equations should we use with the information given? these will both go to find our i and this can be used to find angular acceleration.
01:30
I'm going to use the equation of moment of inertia times angular acceleration.
01:35
You can plug this into one massive equation and i do prefer to do that but it would get very ugly.
01:42
Let's go ahead and first put in what the equation would look like...