在力学中,如果物体处于静止、作匀速直线运动或匀速转动状态,就称这物体处于平衡状态。物体在怎样的条件下才能平衡呢?下面就这个问题进行讨论。物体平衡的条件先从最简单的情况谈起。假设物体仅受到两个外力的作用。如图1所示,物体M受到F_1和F_2的作用。实验指出,如果F_1=-F_2,即这两个力大小相等、方向相反,并 In mechanics, an object is said to be in equilibrium if it is stationary, in a uniform linear motion, or in a uniform rotational state. Under what conditions can the object be balanced? The following discussion is on this issue. The condition of object balance begins with the simplest case. Assume that the object is only affected by two external forces. As shown in FIG. 1, the object M is affected by F_1 and F_2. The experiment pointed out that if F_1=-F_2, that is, the two forces are equal in magnitude and opposite in direction, and