Physics question below?

Question

A roller coaster at an amusement park has a dip that bottoms out in a vertical circle of radius r. A passenger feels the seat of the car pushing upward on her with a force equal to twice her weight as she goes through the dip. If r = 17.0 m, how fast is the roller coaster traveling at the bottom of the dip?

Answer 1

If the force is twice her weight, then the total force is the centrifugal force plus her weight, since she is being acted on by gravity.,

Or
2(m*g)=m*g + mv^2/r
note the mass divides out
subtract one g to get
g=v^2/r
g*r=v^2
v=sqrt(g*r)
plug in the numbers

v=sqrt(9.8*17)
=12.9 m/s

j