两个物体的相互作用力总是大小相等，方向相反，同时出现或消失且作用于同一直线上。

To every action there is always opposed an equal reaction； or， the mutual actions of two bodies upon each other are always equal， and directed to contrary parts.

物体的加速度与所受的合外力成正比，与物体的质量成反比。加速度的方向与合力的方向相同。

The alternation of motion is ever proportional to the motive force impressed; and is made in the direction of the right line in which that force is impressed.

如果物体处于静止状态或作匀速直线运动，只要没有外力作用，物体将保持静止状态或匀速直线运动状态。

Every body continues in its state of rest, or of uniform motion in a right line, unless it is compelled to change that state by forces impressed upon it.