Would someone explain to me when to include the negative into the acceleration a, for F=ma. I know if it is a vector you don't include the sign. But sometimes it seems almost arbitrary in textbooks when they include the negative sign and when they don't. I hope you know what I mean. I know if it is speeding up in the negative direction or slowing down in the positive direction then 'a' is negative, but sometimes it is not given a negative sign. Am I just missing something?(adsbygoogle = window.adsbygoogle || []).push({});

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# Very basic question F=ma

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