Extremely difficult abstract problem...

"A point on the outside of the axle of a truck has a circular motion that can be modeled by a sine curve. If you measure the distance from the axle's center to the bottom of the truck bed, that distance remains constant as long as the truck on a level piece of road. If the truck goes over a bump, the springs absorb the shock but the truck bounces for a while. A truck is moving so that the axle, which is 6 cm in diameter, rotates at 1 rotation per second. As the truck hits a bump, the spring depresses by 80% of the previous bounce as it bounces every half-second.

If the middle of the axle is 30cm, from the bottom of the truck bed, construct a graph illustrating the distance from the point at the top of the axle when the truck hits the bump, to the bottom of the truck bed. What is the equation of the graph"

Here's a picture of the truck: ImageShack: Host and Share your Photos and Videos - abstracttruck.jpg

I know that it is combining an exponential function with a trig function (in this case, sine), but I don't know how to go further from there.

This has really been difficult for me to do, I've been trying for day to solve it and have had no luck, unfortunately. I appreciate all the help I get, thanks guys. (Worried)