1秋千问题一男孩通过交替蹲下和站起的方式来荡秋千.图1所示的是在摆动过程男孩的质心轨迹.当男孩处于站立姿势时,设秋千转轴到男孩质心的距离为r_u;而当男孩处在下蹲姿势时,秋千转轴到男孩质心的距离为r_d.设比值r_d/r_u=21/10=1.072,即男孩站立与下蹲两种姿势时男孩质心相对于秋千转轴的平均距离只变化大约7%. A swing problem A boy swinging by alternating crouching and standing up Figure 1 shows the trajectory of the boy’s center of mass during the swing and when the boy is in a standing position the distance between the swivel axis and the boy’s centroid is r_u; When the boy is in a squatting position, the distance from the swing axis to the boy’s centroid is r_d. The ratio r_d / r_u = 21/10 = 1.072, that is, the average distance of the boy’s centroid relative to the swivel axis when the boy is standing and squatting Only about 7% change.