Why when an object keeps moving at a constant acceleration, it's speed is not always greater than 0?
closed as unclear what you're asking by Martin, AccidentalFourierTransform, user36790, ACuriousMind♦ Oct 30 '16 at 17:05
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I'm not sure I understood your question. If you have an object that has an initial velocity $v_i\neq0$ and has an acceleration directed in the opposite direction of the motion, the object will start decreasing velocity. At a certain point it will reach $v=0$ and after, eventually, it will move backwards.