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1.人体的几何中心在小腹,重心在臀部。拔河人们为了取胜,常采用后仰的姿势,以降低自己的重心。2.人的平均密度约为0.93×103千克/米3,这个密度和水的密度差不多。从理论上讲,人在水中是漂浮的。溺水的人,一是怕水的心理作用,二是身上的附着物使得人体受到重力大于浮力而下沉。3.人的眼睛是一个精巧的变焦距系统。在物距改变时,它能靠改变晶体的弯曲程度来改变焦距,从而看清物体,它的作用相当于一个凸透镜。4.人的眼睛接收到一个物体的光亮到大脑识别这个物体所需时间大约为1/500秒,其明视距离约为25厘米。
1. The geometric center of the human body is on the lower abdomen and the center of gravity is on the buttocks. In order to win, people in tug-of-war tend to adopt a reclining posture to reduce their focus. 2. The average human density is about 0.93 x 103 kg/m3, which is about the density of water. In theory, people are floating in the water. People who drown in water are afraid of the psychological effects of water. Second, attachments on the body cause the human body to sink by gravity that is greater than buoyancy. 3. The human eye is a sophisticated zoom system. When the object distance changes, it can change the focal length by changing the degree of bending of the crystal, so as to see the object, it acts like a convex lens. 4. The human eye receives the light from an object to the brain. The time required to recognize the object is about 1/500 second, and the apparent distance is about 25 cm.