| 释义 |
speed In mathematics, it is useful to distinguish between velocity and speed. First, when considering motion of a particle in a straight line, specify a positive direction so that it is a directed line. Then the velocity of the particle is positive if it is moving in the positive direction and negative if it is moving in the negative direction. The speed of the particle is the absolute value of its velocity. In higher dimensions, when the velocity is a vector v, the speed is the magnitude |v| of the velocity.
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