Gary

When I type a simple formula in the formula bar (e.g., =N62), the cell value shows the 4 characters "=N62" instead of the value of cell N62.

In another cell of the same row, when I entered =L62, it resulted in what I expected--that cell's value was shown as the value in L62.

I've been using Excel for decades and I've never had this happen--it's driving me crazy (well, not really).

Does it count as one of my Answers (but obviously not a Best Answer)?

A few hours ago I answered this question http://answers.yahoo.com/question/index;_ylt=Au8GV...

Now I want to Edit my Answer. I have made my changes, but when I click Submit, I get the screen that says:

Yahoo! Answers is currently unavailable...Yahoo! Answers is experiencing technical difficulties.

So then I press the Back button of my browser (Firefox) to display my Edit screen (whose URL is

http://answers.yahoo.com/question/answerEdit?qid=2...

and try again (after waiting some time). I tried again after letting it "rest" overnight, but I get the same result.

I have started another session in another tab, found the question (it's one of those I've submitted Answers to), opened it for edit, updated the answer, and pressed Submit . . . but I get the same error message.

Anyone have an idea what's wrong? This is a physics question that I've put a lot of effort into; mine is the only Answer so far, and I would really prefer not to lose the opportunity to update it.

Thanks in advance!

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I understand how to determine the sign for a displacement vector defined as

D = Pfinal - Pinitial (where all 3 are vectors)

when time and movement are involved. In this situation it is clear which vector is which: The one which characterizes an earlier point in time is Pinitial and the other is Pfinal.

It is also clear when you're using one as a "reference point":

D = P - Pref

But what about a static situation where there is no time or movement involved, and neither point is the "reference"--you're just using some arbitrary coordinate system?

Specifically, I'm dealing with calculating the electrostatic force F between two point charges p and q using the familiar Coulomb's Law (http://en.wikipedia.org/wiki/Coulomb%27s_law):

F = ke * p * q * Rhat / rpq^2

where:

F = the vector force

ke = Coulomb's constant

p, q = the charges resp. on points .p and .q

rpq = the distance between .p and .q

Rhat = the unit vector parallel to the line connecting .p and .q

and

the lower case p, q, and r are scalars

the upper case F and Rhat are vectors

In this vector equation, the direction of F is determined by Rhat; therefore I need a rule for determining the direction of Rhat:

How do I know whether it goes from .p to .q, or from .q to .p?

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I have been participating in the Physics forum for the past 2 years. By the time voting ends on a Question, the vote count is typically somewhere between 1 and 5 and rarely is it 10 or more.

I recently submitted one of the 2 Answers to this Question: http://answers.yahoo.com/question/index;_ylt=AnkO7... I just checked it, and it now has a total of 84 votes!!

Is this the result of some kind of glitch in the present release of Yahoo!Answers? I find it hard to believe that 80-some different people have looked at this very ordinary physics Question.

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Can anyone point me to an online calculator that correctly evaluates an expression like this?

½ * 2.32e14 * (1.61e-8)²

That is, will it accept:

½ for 0.5

e for "* 10^"

² (superscript 2) for ^2?

It would also be nice if it accepted other such fractions and and exponents, but I would be happy with just ½ and ², because there are so many physics equations having the pattern " ½ * a * b² ".

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I often receive emails urging me to "ask your representative / senator to support Bill xxxx". Before I contact them, however, I'd like to know if they are ALREADY signed on as a co-sponsor. Does anyone know where I can locate that information?

After my question has gone into voting, what are my options? Can I still select a best answer? Or can I vote for the B.A.?

A few days ago the following question was asked in this forum:

"Your friend flies past you at 75% of the speed of light, traveling in a spaceship which she measures at 50 meters end to end. What length do you measure as she goes by?"

The Best Answer (and only answer) was:

"L' = L √(1 - v²/c²)

50 = L √(1 - (0.7c)²/c²)

L = 70.01 meters"

So the answer given is that the observer (stationary?) measures a greater length L (70m) than the friend (passenger) in the spaceship does (L' = 50m).

[Note: I'm not quibbling about the apparent substitution of .7 for .75 in the answer; possibly just an oversight.]

I know about the relativistic mass equation:

(1) m = γ * m0,

where

m = relativistic mass

m0 = rest mass

γ = gamma, the relativistic expansion factor = 1 / √(1 - v² / c²).

In that form, the answer given above seems to be saying that

(2) L = γ * L';

in other words, that L is the relativistic length and L' (50m) is the rest length.

I guess what confuses me is simply substituting L's for the m's in (1).

I would reason that mass is proportional to volume, and volume is proportional to L^3; so that (2) should read as:

(3) L = (γ^1/3) * L' or

(4) L^3 = γ * L' ^3

Can someone explain to me what's going on?

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If I attach a Comment to a Question that's been resolved, will the Asker be notified that a Comment has been added to his/her Question? If not, will anyone be notified?

This is a really simple question! I know I've done it before, but I can't find the right button to push! First one to tell me a procedure I can make work gets 10 . . . and thanks!

I don't have a decibel meter, but the sound level is so high it drowns out everything!

If you have experienced one of their bags (you don't have to buy it--just touch it!) and/or you know the physics behind it, I'd appreciate hearing from you.

On the bottom frame of a Question, there is a Save with a dropdown that includes Add it to your private Watchlist. How do I see what's on my Watchlist? I don't know where to click.

I'm trying to understand the relationship between the ballast and (for example) the lamp--fluorescent, Mh, HPS, HID, etc. I have read the wiki articles on Ballast and Gas-discharge lamp, so I have a superficial understanding of why they're needed.

But suppose I'm building a system which needs Mh or HPS lamps, such as a hydroponic plant growing system. Once I design the desired physical layout and figure out how many lights I need, how do I figure out my ballast requirements?

What electrical parameters do I have to match (e.g., watts, volts, amps, ohms, etc.)?

If I use multiple ballasts, how are those "ganged" together?

Can I use an over-designed ballast (e.g., 1000W ballast for 600W total of lights, 220V ballast for 110V lights)?

Can I ever use an under-designed ballast?

I hope you get the idea of what I'd like to know!