00:01
Our goal is to write an equation, a differential equation that follows this english sentence.
00:09
What i do like is that math can usually be translated to symbols fairly easily with a short sentence like this.
00:19
So here the short sentence has two important things, the rate of change of radius.
00:29
And then there is an is statement.
00:32
So that is our equal sign.
00:35
And on the equal sign, on the other side of the equal sign, is the other phrase that we are going to have to model with math.
00:45
So rate of change of radius, we are going to, first of all, give radius a symbol little r.
00:51
That seems appropriate.
00:54
And rate of change is fairly straightforward too.
00:59
Usually the derivative of the variable with respect to time.
01:05
Time is what changes things.
01:09
So with respect to time...