专业物理英语翻译

Bodies forming a mechanical system may interact with one another and with bodies not belong to given system. Accordingly the forces acting on the bodies of a system can be divided into internal and external ones. We shall define internal forces as the forces with which given body is acted upon by the other bodies of the system and external forces as those produced by the action of bodies not belonging to system. if external forces are absent,the relevant system is closed.物体形成一个机械系统可能会与另一个物体属于给定的系统。因此对一个系统的体力可分为内部的和外部的。我们将定义内部力的力量与给定的物体受到外力的系统和其他机构的那些不属于系统机构的作用而产生的。如果外部的力是不存在的，相关的系统关闭。

There are functions of coordinates and velocities of the particles forming a system for closed systems that retain constant values upon motion. These functions are called motion integrals.还有的坐标和形成一个封闭的系统，保持恒定值对运动系统的粒子速度的功能。这些功能被称为运动积分。

The number of motion integrals that can be formed for a system of N particles between which there are no rigid constraints is 6N-1.Only those of them are of interest to us that have the property of additively. This property consists in that the value of a motion integral for a system comprising parts whose interaction may be disregarded equals the sum of the values for each part. There are three additive motion integrals. The first is called energy,the second--momentum,and the third--angular momentum.一些运动积分，可以形成一个系统的N个粒子之间没有刚性约束6n-1.仅仅那些让我们感兴趣的属性相加。此属性包含在一个运动积分值系统的相互作用可以忽略不计，包括部分相等的值的总和为每个部分。有三种运动积分。第一个被称为能量，第二和第三分别为动量，角动量。

Vector quantity A quantity that has both magnitude and direction.Examples:force,velocity,acceleration,and momentum.矢量一个量它有大小和方向。例如：力，速度，加速度，动量。

Scalar quantity A quantity that has magnitude,but no direction.Examples:mass,volume,and speed.标量一个量它有大小但是没有方向。例如：质量，体积和速率。

Vector An arrow drawn to scale used to represent a vector quantity.矢一个标有刻度的箭头去代表矢量。

Motion A change of position. 运动位置的改变。

Speed The distance traveled per time. 速率距离与所用时间比。

Velocity The rate of change position and the direct of the motion.Velocity is a vector quantity. 速度沿速度方向位移的变化率。它是一个矢量。

Acceleration Time rate of velocity:Acceleration=change in velocity/time it takes for change.加速度速度的变化率，加速度=速度的变化量/这段时间。