Lesson1 1、the branch of scientific analysis, which deals with motions, time, and forces, is called mechanics and is made up of two parts, statics and dynamics. Statics deals with the analysis of stationary systems, i.e., those in which time is not a factor, and dynamics deals with systems, which change with time. 对运动时间和作用力作出科学分析的分支成为力学。他由静力学和动力学两部分组成。静力学对静止系统进行分析，即在其中不考虑时间这个引述，动力学对事件而变化的系统进行分析。 2、Any two such forces acting on a body constitute a couple. The arm of the couple is the perpendicular distance between their lines of action, and the plane of the couple is the plane containing the two lines of action. 作用在一个刚体上的两个这样的的里构成一个力偶。力偶臂是这两个条作用线之间的垂直距离，力偶面是包含着两条作用线的平面。 3、Mechanics deal with two kinds of quantities: scalars and vectors. Scalar quantities are those with which a magnitude alone is associated. Examples of scalar quantities in mechanics are time, volume, density, speed, energy, and mass. Vector quantities, on the other hand, possess direction as well as magnitude. Examples of vectors are displacement, velocity, acceleration, force, moment, and momentum. 力学涉及两种类型的量，标量 和矢量。标量是那些只有大小的量。在力学中标量的例子有时间、体积、密度、速率、、能量和质量。另一方面，矢量既有大小又有大小又有方向。矢量的例子有位移、速度、加速度、力、力矩、动量。 Lesson2（此课后面没翻译，翻译的不太准确谅解） 1 、The turning of a part in a lathe is another example of several forces in action.（as shown in figure1） 车床车削是一些力在起作用的另一个例子。figure1(如图)。 2 、If this workpiece is held between the centers of the lathe, the centers exert a compressive force against the work. 如果这个工件在放在车床中心之间,中心车床对...
