# Homework Help: Centripetal Forces Help please

1. Jan 7, 2010

### Instanbul

1. The problem statement, all variables and given/known data
How much force is needed to swing a 4kg mass in a 3m radius horizontal circle so that each cycle takes exactly 2 seconds. Answer is 118N but the problem is how do I get to that...

2. Relevant equations
V=2Pir/T F=mv^2/r

3. The attempt at a solution
I tried using F=mv^/r one but I got nowhere close my teacher just solves problems without explaining at all and I have no clue how to solve it except find numbers.

2. Jan 7, 2010

### rock.freak667

I one cycle takes 2 seconds, how many cycles are in one second? Hence what is the angular velocity of the bat?

3. Jan 7, 2010

### Instanbul

It doesn't say thats all the info that the problem gives me.

4. Jan 7, 2010

### rock.freak667

I am quite sure you can find the the number of cycles in 1 second given, that 1 cycle takes 2 seconds.

5. Jan 7, 2010

### Instanbul

Aren't I looking for the force of the swing?

Last edited: Jan 7, 2010
6. Jan 7, 2010

### rock.freak667

Yes but you need to get the periodic time to get F.

7. Jan 7, 2010

### Instanbul

Oh I get it now thank you so much.