Register to reply

Question about this problem and Walter Lewin's video

by flyingpig
Tags: lewin, video, walter
Share this thread:
flyingpig
#1
Mar30-11, 05:03 PM
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 [tex]-27\mu N \hat{i}[/tex]

From Walter Lewin's method, I got [tex]+27\mu N \hat{i}[/tex]. Help?


3. The attempt at a solution
Phys.Org News Partner Science news on Phys.org
Experts defend operational earthquake forecasting, counter critiques
EU urged to convert TV frequencies to mobile broadband
Sierra Nevada freshwater runoff could drop 26 percent by 2100
flyingpig
#2
Mar31-11, 11:47 AM
P: 2,568
Is no one answering because no one is bothered to watch the video lol?
flyingpig
#3
Apr5-11, 07:05 PM
P: 2,568
Please...

Antiphon
#4
Apr5-11, 08:03 PM
P: 1,781
Question about this problem and Walter Lewin's video

Flip the paper over. Then your i-hat will point the same way his does.
SammyS
#5
Apr5-11, 10:35 PM
Emeritus
Sci Advisor
HW Helper
PF Gold
P: 7,819
Quote Quote by Antiphon View Post
Flip the paper over. Then your i-hat will point the same way his does.
@Antiphon: Nice answer!

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

LOL
SammyS
#6
Apr5-11, 10:48 PM
Emeritus
Sci Advisor
HW Helper
PF Gold
P: 7,819
Seriously, Mr. Lewin clearly states that the force is toward the left.

Therefore, it's in the [tex]-\hat{i}[/tex] direction.
flyingpig
#7
Apr6-11, 02:32 PM
P: 2,568
Quote Quote by Antiphon View Post
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?
SammyS
#8
Apr6-11, 05:21 PM
Emeritus
Sci Advisor
HW Helper
PF Gold
P: 7,819
Use thinner paper, write darker and/or use a light table.
flyingpig
#9
Apr6-11, 05:36 PM
P: 2,568
...

but what if I want to do it mathematically?
SammyS
#10
Apr6-11, 07:37 PM
Emeritus
Sci Advisor
HW Helper
PF Gold
P: 7,819
Quote Quote by SammyS View Post
Seriously, Mr. Lewin clearly states that the force is toward the left.

Therefore, it's in the [tex]-\hat{i}[/tex] direction.
Did you see this?
Andrew Mason
#11
Apr6-11, 11:24 PM
Sci Advisor
HW Helper
P: 6,679
Quote Quote by flyingpig View Post
The answer key said the force is [tex]-27\mu N \hat{i}[/tex]

From Walter Lewin's method, I got [tex]+27\mu N \hat{i}[/tex]. Help?
How do you get the force going to the right?

AM


Register to reply

Related Discussions
Is MIT Prof. Lewin wrong about Kirchhoff's law? Classical Physics 347
Prof. Walter Lewin's best lines ;) General Discussion 5
Question about Walter Brattain’s field-effect transistor principle. Classical Physics 8
MIT's Walter Lewin's twice surprises the EE professors! (fun) General Physics 13
Kirchhoff's 2nd law wrongly used or not? Lewin vs all college books General Physics 6