That's another way of saying maintaining velocity if it's not acted upon by a force.

这就是不受外力作用时,速度保持不变的另一种说法

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The Law of Inertia says that, "If a body has no forces acting on it, then it will remain at rest if it was at rest to begin with, or if it had a velocity to begin with, it will maintain that velocity."

惯性定律就是,"如果一个物体不受外力作用,那么静止的物体依然保持静止,如果物体有个初速度,那么就保持此速度不变"

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