# Question on flows

1. Jun 2, 2013

### 1670frank

1. The problem statement, all variables and given/known data

θ'=1-cosθ If we have the flow starting at θ(0)=A, determine the amount of time, T(A), that it takes to reach θ=pi and what is the leading behavior as A approaches 0.

2. Relevant equations

3. The attempt at a solution
Well, in my book, they give an equation T=2pi/w where w is the velocity of θ'. T means in this equatio the time the flow requires to go a full circle back to the initial point back to 0. Not sure how to use this equation in this case I think they got this equation by saying that θ(t) changes by 2pi meaning the travel distance while in this case the travel distance is pi-A so T=(pi-A)/w but not exactly sure about this. I really need help with this...

2. Jun 3, 2013

### haruspex

By θ' I assume you mean dθ/dt, right? Can you solve that differential equation?

3. Jun 5, 2013

### 1670frank

Yes, you can write it as you say

4. Jun 5, 2013

### haruspex

I also asked whether you can solve the DE. I don't understand what you mean by "the velocity of θ' "