Question about this problem and Walter Lewin's video

  • Thread starter flyingpig
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In summary: Lewin stated that the force in the problem was towards the left, so it should be in the negative i-hat direction. However, the answer key gave a positive i-hat direction. The solution is to flip the paper over so that your i-hat direction matches the one in the video. This can be done by using thinner paper, writing darker, or using a light table. Alternatively, one can also solve the problem mathematically by using vector operations to determine the direction of the force.
  • #1
flyingpig
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Homework Statement



https://www.youtube.com/watch?v=4zb0t4H0Kec

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

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?

The Attempt at a Solution

 
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  • #2
Is no one answering because no one is bothered to watch the video lol?
 
  • #3
Please...
 
  • #4
Flip the paper over. Then your i-hat will point the same way his does.
 
  • #5
Antiphon said:
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
 
Last edited:
  • #6
Seriously, Mr. Lewin clearly states that the force is toward the left.

Therefore, it's in the [tex]-\hat{i}[/tex] direction.
 
  • #7
Antiphon said:
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?
 
  • #8
Use thinner paper, write darker and/or use a light table.
 
  • #9
...

but what if I want to do it mathematically?
 
  • #10
SammyS said:
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?
 
  • #11
flyingpig said:
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
 

1. What is the problem discussed in Walter Lewin's video?

The problem discussed in Walter Lewin's video is the concept of conservation of energy and its application in solving physics problems.

2. How does Walter Lewin explain the problem in his video?

Walter Lewin explains the problem by using real-life examples and demonstrations, as well as mathematical equations and diagrams, to illustrate the concept of conservation of energy.

3. What are some key takeaways from Walter Lewin's video?

Some key takeaways from Walter Lewin's video include the understanding of the law of conservation of energy, how to apply this law to solve physics problems, and the importance of understanding and mastering fundamental concepts in physics.

4. How can I use the information from Walter Lewin's video in my own studies?

You can use the information from Walter Lewin's video to deepen your understanding of the concept of conservation of energy and apply it to solve physics problems. You can also use his teaching methods and examples as a guide for your own studies.

5. Is this video suitable for beginners in physics?

Yes, this video is suitable for beginners in physics as Walter Lewin explains the concept of conservation of energy in a clear and easy-to-understand manner, using relatable examples and step-by-step explanations. However, some mathematical knowledge may be required to fully grasp the concept and solve the practice problems shown in the video.

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