方向为x正轴方向，在碰撞前，它有一定动量。

Let this be the direction of increasing x, and so before the collision I have a certain amount of momentum.

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碰撞前没有动能。

There was no kinetic energy before...

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本文根据动量平衡和动量守恒定律的基本原理，提出了两种推算碰撞前汽车动量或碰撞速度的图解方法。

Based on momentum balance and the law of momentum conservation, two new graphic methods are developed to determine the pre-impact vehicle momentum or collision speed in this paper.

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