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### Topic: Some questions  (Read 8902 times)

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#### abhaymv

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##### Some questions
« on: February 25, 2009, 07:19:45 AM »
Is weight an example for a quantity Which has direction but is not a vector?

A thin metal ring has a diameter 0.20 cm and mass 1 kg, Calculate the moment of inertia about an axis passing through any tangent. Please write all the steps and formulaes?

A sonometer wire of length 30cm vibrates in the second overtone so How do you represent it pictorically and What is the difference between two points of the string having phase differance Pi?

If a violin string resonates at fundemental frequency of 196 Hzwhere along the string must you place your finger so that the fundemental frequency becomes 440 Hz and the length of string is 40cm?

#### Borek

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##### Re: Some questions
« Reply #1 on: February 25, 2009, 09:27:06 AM »
You just don't ask. You try, you tell us what you did, we push you in the right direction.
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#### abhaymv

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##### Re: Some questions
« Reply #2 on: February 25, 2009, 09:37:47 PM »
Is weight an example for a quantity Which has direction but is not a vector?

A thin metal ring has a diameter 0.20 cm and mass 1 kg, Calculate the moment of inertia about an axis passing through any tangent. Please write all the steps and formulas?

A sonometer wire of length 30cm vibrates in the second overtone so How do you represent it pictorially and What is the difference between two points of the string having phase difference Pi?

If a violin string resonates at fundamental frequency of 196 Hz,where along the string must you place your finger so that the fundamental frequency becomes 440 Hz and the length of string is 40cm?
In the weight problem, I referred a few books, it said current, time etc was examples for non vector quantities having no direction, nothing about weight...
In the second question,I think I should use parallel axis theorem, finding the moment of inertia about centre and using theorem, find it about diameter.Is it correct?

Next question,I think the correct way of representing it would be through the pictorial representation of third harmonic wave, but I'm not sure.I think there is no difference between a phase difference pi, is there?Doesn't it reach in the same place?

I have no idea about the last question.
Sorry, but i am a mare pre degree first year.

#### Borek

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##### Re: Some questions
« Reply #3 on: February 26, 2009, 03:06:25 AM »
1. What is weight definition?

2. Most likely you are right.

3. Perhaps it asks about the distance between these points?

4. Any relationship between string length and frequency?
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#### abhaymv

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##### Re: Some questions
« Reply #4 on: February 27, 2009, 06:40:43 AM »
1.MassXGravity, gravity acts downward.So does this mean that weight is an example?

4.There is, I think, but how does it help you with where to place your hand?

#### Borek

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##### Re: Some questions
« Reply #5 on: February 27, 2009, 07:12:29 AM »
1.MassXGravity, gravity acts downward.So does this mean that weight is an example?

What is "gravity"?

Quote
4.There is, I think, but how does it help you with where to place your hand?

have you ever played guitar or violin? Or have you at least seen someone playing? You use your finger to shorten the vibrating part of the string.
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#### Yggdrasil

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##### Re: Some questions
« Reply #6 on: February 27, 2009, 10:01:47 AM »
1.  A weight is essentially a force.  Forces are represented by vectors.

4.  By placing your finger on a string, you prevent the string from moving at that position and thus create a node in the vibrations of the string.

#### Borek

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##### Re: Some questions
« Reply #7 on: February 27, 2009, 10:34:36 AM »
1.  A weight is essentially a force.  Forces are represented by vectors.

I hoped to guide abhaymv to this conclusion.
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#### abhaymv

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##### Re: Some questions
« Reply #8 on: February 28, 2009, 11:37:02 PM »
Violin question:
I know the equation f=n(v/2L)
where f is the frequency.
Applying this,
196=n(v/80)
440=n(v/2L)
I don't know how to solve further.
Is the equation wrong?