# Centripetal force help

1. Nov 1, 2006

### wakejosh

first off, thanks for all the help. My physics book got taken when my car got broken into and my backpack was taken. I have an old book and my pages dont coencide with my homework. everyone has been a big help. with that,, i just have two final questions about centripetal force:

1. A ventilation fan has blades 0.25 m long rotating at 2 rad/s.
What is the centripetal
acceleration of a point on the outer tip of a blade?

2. An airplane is a wide sweeping "outside" loop can create zero "g"
(weightlessness) inside
the aircraft cabin. What must be the radius of curvature of the
flight path for an aircraft
moving at 70 m/s to create a condition of "weightlessness" inside
the aircraft?

Im really not sure where to start with these, although I do realize that I need to account for gravity, just not sure what kind of equation im looking for.

2. Nov 1, 2006

### BishopUser

$$A_{centripital} = \frac {v^2} {r}$$ don't put angular velocity into that either. That should get you started atleast

3. Nov 1, 2006

### wakejosh

is the v^2 the velocity squared meaning the rad/s, or do i need to convert that to something else?

4. Nov 1, 2006

### BishopUser

rad/s is an angular velocity, you need to somehow convert that into m/s

5. Nov 1, 2006

### wakejosh

ok, so for 1 do i do this:

.25m * 2 rad/s = .5

.5^2 / .25 = 1 m/s/s

is this correct for 1?

Last edited: Nov 1, 2006
6. Nov 1, 2006

### wakejosh

and for 2:

9.8 = 70^2 / r

r = 500 m

are these correct?

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