牛顿第一定律是什么？请以markdown方式呈现。
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Newton's First Law of Motion, also known as the law of inertia, can be described as follows:

Newton's First Law: An object at rest stays at rest and an object in motion stays in motion with the same speed and in the same direction unless acted upon by an unbalanced force. 

Here is the markdown version:
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**牛顿第一定律（惯性定律）**：任何物体都会保持其静止状态或匀速直线运动状态，除非受到外力迫使它改变这种状态。
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