I think it's a pretty simple question. Let's say we're talking about a moving elevator in which a person stands on a digital balance. The textbook tells me to treat the downward direction as positive, so the value of acceleration is 9.8 m/s^2 instead of -9.8m/s^2(adsbygoogle = window.adsbygoogle || []).push({});

I'm asked to find out the acceleration of the elevator when the person's weight appears to be 0.75 times of its normal weight. I got a negative value, which is the correct answer. Then the book tells me that since it's negative, it means that the elevator is going down. But I thought that the downward direction is treated as positive!

(I think the book is correct. I just don't understand what the negative sign means.)

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# Negative and positive results when dealing with Newton's Laws

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