1. Mar 30, 2011

flyingpig

1. The problem statement, all variables and given/known data

http://img4.imageshack.us/img4/7388/38804877.th.png [Broken]

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

Last edited by a moderator: May 5, 2017
2. Mar 31, 2011

flyingpig

Is no one answering because no one is bothered to watch the video lol?

3. Apr 5, 2011

4. Apr 5, 2011

Antiphon

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

5. Apr 5, 2011

SammyS

Staff Emeritus

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

LOL

Last edited: Apr 5, 2011
6. Apr 5, 2011

SammyS

Staff Emeritus
Seriously, Mr. Lewin clearly states that the force is toward the left.

Therefore, it's in the $$-\hat{i}$$ direction.

7. Apr 6, 2011

flyingpig

If you flip the paper over, how can you see your work?

8. Apr 6, 2011

SammyS

Staff Emeritus
Use thinner paper, write darker and/or use a light table.

9. Apr 6, 2011

flyingpig

...

but what if I want to do it mathematically?

10. Apr 6, 2011

SammyS

Staff Emeritus
Did you see this?

11. Apr 6, 2011

Andrew Mason

How do you get the force going to the right?

AM