Centripetal acceleration acting on a parcel

[cmcd]

Homework Statement

A parcel sits on a seat angled θ to the horizontal. The car is traveling along a local radius of curvature of 80m and is traveling 20m/s at the dip. For what value of theta will the parcel not slip?

Will someone check that my force diagram is correct?
Thanks,
cmcd

http://s1372.photobucket.com/user/cmcdona22/media/001_zps29188e8a.jpg.html

 

[cmcd]

*.*.

 

[cmcd]

$$\rho_0$$

 

[cmcd]

$$\rho(h)=\rho_0\exp^-\frac{\rho_0g_ph}{p_0}$$