How do you know if velocity is changing?

To figure out if velocity is changing, you must know whether the speed or the direction changes, as one of these is required in order for velocity to change. Velocity can also change in both speed and direction change. Constant velocity is when neither speed nor direction change, but continue on in the same way indefinitely. Velocity is a vector, with length and direction being its two components. Speed is considered to be the length.
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Q&A Related to "How do you know if velocity is changing?"
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