crack shot Exploratorium Museum Exhibits

The distance from a moving point on a plane to a fixed point (focus) is equal to the distance to a fixed line (directrix), and a parabola is the set of all moving points that meet these conditions. The surface obtained by rotating a parabola around its axis is called a paraboloid.
The exhibit is based on the optical focusing principle of the parabola: the light emitted from the focal point is parallel to the main axis after being reflected by the parabola. After the ball is released from a high place, it will collide with the paraboloid and bounce to the focal point of the paraboloid after falling freely, and then ring the bell at the focal point.