by flyingpig
Tags: lewin, video, walter
 P: 2,568 1. The problem statement, all variables and given/known data Uploaded with ImageShack.us The problem is EXACTLY the same. But one thing concerns me. The answer key said the force is $$-27\mu N \hat{i}$$ From Walter Lewin's method, I got $$+27\mu N \hat{i}$$. Help? 3. The attempt at a solution
 P: 2,568 Is no one answering because no one is bothered to watch the video lol?
P: 1,781

Flip the paper over. Then your i-hat will point the same way his does.
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 Quote by Antiphon Flip the paper over. Then your i-hat will point the same way his does.

@fp: He means left to right, not top to bottom.

LOL
 PF Patron HW Helper Sci Advisor Emeritus P: 7,076 Seriously, Mr. Lewin clearly states that the force is toward the left. Therefore, it's in the $$-\hat{i}$$ direction.
P: 2,568
 Quote by Antiphon Flip the paper over. Then your i-hat will point the same way his does.
If you flip the paper over, how can you see your work?
 PF Patron HW Helper Sci Advisor Emeritus P: 7,076 Use thinner paper, write darker and/or use a light table.
 P: 2,568 ... but what if I want to do it mathematically?
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 Quote by SammyS Seriously, Mr. Lewin clearly states that the force is toward the left. Therefore, it's in the $$-\hat{i}$$ direction.
Did you see this?
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 Quote by flyingpig The answer key said the force is $$-27\mu N \hat{i}$$ From Walter Lewin's method, I got $$+27\mu N \hat{i}$$. Help?