# Calculating Centripetal force

1. Oct 28, 2008

### Fractal314

1. A bird of mass 0.211kg pulls out of a dive, the bottom of which can be considered to be a circular arc with a radius of 25.6m. At the bottom of the arc, the bird's speed is a constant 21.7m/s. Determine the magnitude of the upward lift on the bird's wings at the bottom of the arc.

I am pretty sure that Fc= -4(pi squared)(r)(m)(f) / Tsquared

and... Fc= -mv squared / r

r= radius, m= mass, Fc = centripetal force

3. Ok so I don't understand what it means by "pulling out of a dive", I mean is that supposed to be part of the arc? This question is put under the heading centripetal force in my textbook but I don't understand how it is centripetal. Furthermore, if all is well, does it come down to the question being as simple as subbing in the values to the equation I have here.

Also, can anybody tell me how the centripetal force equation is derived from F=MA? I am lost on that too.

2. Oct 28, 2008

### Epsillon

On the bottom of the dive there is the upward lift force pulling it up and also gravity pulling the bird down. so Fc= Upward lift force - Fg