Eise Posted November 27, 2019 Share Posted November 27, 2019 (edited) 41 minutes ago, TakenItSeriously said: Your kidding right? You do realize that when you take the square root of any number you get a positive and negative result right? But first, this is physics, not mathematics. One must always check if both solutions make sense physically. Second, the direction of the velocity has nothing to do with the choice of the positive or the negative result, as Strange already showed, because you must use v2. So third, what do you get if you take the negative value as possible outcome? Say you compare two sticks, one flying in the opposite direction of the other, with the same speed. Due to the length contraction, one stick has for you a length of -0.5L, the other +0.5L. Which one is longer? 😈 So what is the physical meaning of a negative length? Edited November 27, 2019 by Eise Link to comment Share on other sites More sharing options...
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