The body without deformation is called a rigid body. 铁石心肠 不可塑造 Its motion includes usually two types: (1) translation(平动); (2) rotation(转动)。 Examples: dancing, stang, motion of Earth, motion of electron in the atom world
The body without deformation is called a rigid body. (1) translation（平动）; (2) rotation（转动）。 Examples: dancing, skating, motion of Earth, motion of electron in the atom world,……. Its motion includes usually two types: 铁石心肠 不可塑造
851 Motion of a Rigid body 刚体的平动、转动和定轴转动 1. The model of a rigid body刚体模型 Rigid body(刚体): an ideal mode The distance between two points in a rigid body maintains constant forever. Thus the body has a perfectly definite unchanged shape and size. 刚体是一种理想模型:刚体是在任何外力作用下任意两点间 均不发生位移,形状大小均不发生改变的物体
1. The model of a rigid body 刚体模型 Rigid body（刚体） : an ideal model 刚体是一种理想模型：刚体是在任何外力作用下任意两点间 均不发生位移，形状大小均不发生改变的物体。 §51 Motion of a Rigid Body 刚体的平动、转动和定轴转动 The distance between two points in a rigid body maintains constant forever. Thus the body has a perfectly definite, unchanged shape and size
2. Translation Rotation of a rigid body 刚体的平动和转动 (1) Translation(平动) 看成质点 All particles describe parallel (平行) paths, and have the same velocity acceleration Therefore, the motion of any point of the body can represent the translational motion of entire(整个) rigid body. 水平飞行 (平动:刚体上所有点的运动轨迹都相, 可当作质点来处理。)
2. Translation & Rotation of a rigid body 刚体的平动和转动 (平动：刚体上所有点的运动轨迹都相， 可当作质点来处理。) All particles describe parallel （平行） paths, and have the same velocity & acceleration. Therefore,the motion of any point of the body can represent the translational motion of entire（整个） rigid body. (1) Translation（平动）: 水平飞行 看成质点
(2) Rotation: All particles describe circular paths around a line called the axis (ti) which may fixed or may changing its position during the motion. (转动:刚体上各点都绕某一轴 作圆周运动,转轴可能是固定 的也可能在运动中改变位置。) ∵ 圆周运动
All particles describe circular paths around a line called the axis（轴） which may fixed or may changing its position during the motion. (2) Rotation: (转动：刚体上各点都绕某一轴 作圆周运动，转轴可能是固定 的也可能在运动中改变位置。) 圆周运动