Force and Motion Ferris wheel problem

[bosburn93]

Homework Statement

A circular-motion addict of mass 80 kg rides a Ferris wheel around in a vertical circle of a radius 10 m at a constant speed of 6.1 m/s. (a) What is the period of motion? What is the magnitude of the normal force on the addict from the seat when both go through (b) the highest point of the circular path and (c) the lowest point?

Homework Equations

F=ma
a= v^2/r
v=2(pi)r/T

The Attempt at a Solution

(a) v=2(pi)r/T T= 10.3 s
(b) i tried N=mg + m(v^2/r)
i ended up getting 1081.68 but the book says the answer is 490

 

[grzz]

A FBD is ALWAYS IMPORTANT.

Use f(net) = ma at the highest point, in the direction towards the centre of the circle and ... you immediately notice your mistake.