There are two kinds of skateboards for the combination slide, one is straight and the other is curved, and its sliding surface is the rotary line. Suppose the height of the two slides is the same. When two children of exactly the same weight slide down from the apex of the slide at the same time, the children who arrive at the ground first are not the children on the straight skateboard, but the children on the surface of the rotary line. Because children can slide on slides because of gravity. When the slope of the skateboard surface is different, the magnitude of the gravitational force applied in the sliding direction is also different. The greater the gravitational component, the greater the acceleration of the slip, and the faster the speed increases. As the slide slides down the slide, the acceleration of the slide remains unchanged and the speed increases steadily. Sliding down the roller line slide, the slope of the first section of the skateboard is very large, so that the sliding children get very slow in a very short time. Although, in the latter half of the decline, the slope gradually became smaller and the speed increased slowly, but the speed of decline at this time has become very large.

Therefore, the slide along the surface of the spinning wheel plate slides down at an average speed throughout the sliding phase. Even if the length of the slider of the rotary line slide is larger than the length of the straight slide, the time to slide along the rotary line slide is shorter than that of the straight slide. This is proved mathematically and physically. That is, under the same conditions of the same height, the time to slide along the winding line is the shortest.