Proving Negative G-Forces with an Example

[BlueBiro]

Hi, nice forum. I was thinking how I would go about proving with an example, that negative Gs are occurring?

Homework Statement

Say a stunt pilot is doing a maneuver that will expose him to negative Gs. It could look like this:
[URL]http://upload.wikimedia.org/wikipedia/commons/5/57/Aeros_fig_englishbunt.svg[/URL]
Let his mass = 70kg and v = 60 m/s
These can be modified if you like

Homework Equations

Fc = (mv²)/r & F = ma

or ac = v²/r ?

The Attempt at a Solution

I was hoping to be able to finish with something like: if r > 1024m then he experiences -Gs but the answer is always positive. The only thing that could be -ive is velocity but it's squared. Am I attacking this wrong?

 

[SteamKing]

It's not clear from your diagram what the direction of travel is.

 

[BlueBiro]

He would be traveling from the point (the top).
Using the above velocity, with a radius of 150m, his accel would = 24 ms² ≈ 2.4 g's.
Would I be correct in saying that when he is travveling vertically downwards that would be 2.4 negative g's?