A paintball gun is shot at the side of a wheel of a passing car. The paintball leaves a mark on the tire 5cm in from the edge of the tire. The radius of the tire is 20cm. As the car continues to drive the paintball splatter rises and falls like a periodic function. At its current speed the tire is making four revolutions every second. Determine the equation of a sinusoidal function that will model this situation, assuming that the splatter is at its maximum height at time zero.