加速度的方向与合力的方向相同。
The direction of the acceleration is the direction of the net force.
除非有一合力作用于物体上，否则物体的方向是不会发生变化的。
There is no change in the motion of a body unless a resultant force is acting upon it.
在这个和那个方向上的合力必定为零。
The summation of forces in this and that directions must be zero.
那么单摆在振动过程中，切向力、法向力及合力的大小和方向是否在变化?。
Do the tangential force, the mormal force, the resultant force and their directions during oscillation of a simple pendulum change?
沿着纤维长度有很强结合力的共价结合在这个方向上给予复合材料很高的模量，因为要损坏或拉伸纤维就必须破坏或移除这种结合。
The strong covalent bonds along the fiber's length give them a very high modulus in this direction because to break or extend the fiber the bonds must also be broken or moved.
而这些成就的取得，绝不是由某种单一力量所决定的，而是由多种复合力量所形成的历史的合力方向所决定的。
But what these achieve obtain, anything but from what single a certain strength decide, but from various compound what the resultant force direction of history become by strength decides.
换句话说，因为没有竖直方向的合力，所以线动量的竖直方向仍为零。
In other words, the vertical component of its linear momentum remains zero, since there is no resultant vertical force.
若使合力总是指向重力的反方向，则这个合力是一种无支撑的悬浮力。
If the direction is opposite with gravity, the resultant force is a levitation force.
由此得出，决定井眼轨迹的是钻头合位移方向，而不必是合力方向。
The trajectory of bore hole is proved to be formed by the resultant displacement of the bit instead of the resultant force.
对动态电荷群的研究得知能够实现这种悬浮力。 较简单的情形是只要两个动态点电荷满足三个条件，它们各自受到的力就会指向同一方向，力的大小按正弦规律变化，合力不为零且稳定不变。
A simple type is that the forces on two dynamic point charges have the same direction, the scale of the forces are changeable with sine regularity and its' resultant force is stable and nonzero.
对动态电荷群的研究得知能够实现这种悬浮力。 较简单的情形是只要两个动态点电荷满足三个条件，它们各自受到的力就会指向同一方向，力的大小按正弦规律变化，合力不为零且稳定不变。
A simple type is that the forces on two dynamic point charges have the same direction, the scale of the forces are changeable with sine regularity and its' resultant force is stable and nonzero.
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