How Do You Calculate the Force on a Ferris Wheel Rider at a Specific Point?

[the_nile_song]

Just before finals you decide to visit an amusement park set up in the Metrodome. Since it is a weekend, you invite your favorite niece along. She loves to ride on a Ferris wheel, and there is one at the amusement park. The Ferris wheel has seats on the rim of a circle with a radius of 25 m. The Ferris wheel rotates at a constant speed and makes one complete revolution every 20 seconds. While you wait, your niece who has a mass of 42 kg, rides the Ferris wheel. [B]To kill time you decide to calculate the total force (both magnitude and direction) on her when she is one quarter revolution past the highest point. [/B]Because the Ferris wheel can be run at different speeds, you also decide to make a graph which gives the magnitude of the force on her at that point as a function of the period of the Ferris wheel.

please help me..Of course I know circular motion,centripetal acceleration etc..but I can't understand this bold part.

 

[Doc Al]

The bold part just specifies the location of the person at the moment of interest. You need that to specify the direction of the force on her. (Draw yourself a diagram.)