i'm stuck on this question and i have no clue how to slove it to get the equations.

A point on the outside of the axle of a truck has a circular motion that can be modelled by a sine curve.if you measure distance from the axle's centre to the bottom of the truck, that distance remains constant as long as the truck is 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 20 cm and then continues to depress by 80% of the percious bounce as it bounces ever half second.

if the middle of the axle is 30 cm from the bottom of the truck, what is the equation that repersents the distance from a point on the outside of the axle to the bottom of the truck