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# Thread: FCK!!!! Brain lock on physics question

1. ## FCK!!!! Brain lock on physics question

Workin on some physics hw for the past couple hours and my brain is ready to take a sh.it.....

A nonconductor has an internal electric field that varies radially
E = 5.2 * (V/m^4) * r^3 * (r_vector)

a) Find the E force on an electron at r = .25m

b) Find the change in C from r = 0 to r = .24

c) The electron is released from rest at r = .25m, Find the speed of the electron at r = 0

2. Oh yea, let me say thanks in advance..... Im not even lookin for free-bies here, even a couple hints would probably help

3. magnetic fields? am i to assume this is a spehere? is that all there is to the detail of the question?
Last edited by Psychotron; 10-20-2004 at 08:03 PM.

4. Yup thats why I am stumped, doesnt show a picture at all either

5. whats V? I'm assuming m is distance in meters?

And where the F is C in there? lol

6. yea, um bump

7. V=voltage

8. Are you supposed to find it in terms of V cuz i think youve got too many unknowns in one equation... you dont know E and you dont know V

9. Originally Posted by AandF6969
Are you supposed to find it in terms of V cuz i think youve got too many unknowns in one equation... you dont know E and you dont know V
This is why im stumped.... I dont know m either.

I think this is supposed to represent something like an extension cord, or power cord, etc... where m is the length of the extension cord, r is the radius, V is the voltage going through cord, etc. That is all I can think of. Im not sure how to manipulate this formula though to find out E for the first part. I emailed the teacher, hopefully he gets back to me letting me know he forgot to add another part to the question.

10. E=mc^2

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Buy the sol'ns manual you cheap bastard

12. Originally Posted by Powrlftr
Buy the sol'ns manual you cheap bastard
LOL, he made it up along with a crapload of others and gave us his own little worksheet.... its not due for a grade, but im **** sure positive ill see somethin like this on an exam.

13. If i knew there was going to be this much physics involved in getting a BA in engineering I woulda went into MIS or something, lol.

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Originally Posted by OSTIE
If i knew there was going to be this much physics involved in getting a BA in engineering I woulda went into MIS or something, lol.
LoL, I hope you are joking about thinking engineering wasn't mostly physics. You should've done what I did to avoid the physics, become a synthetic organic chemist. The toughest math I do is simple arithmetic.

15. Now that i think about it m is usually mass... not meters or length

16. Originally Posted by AandF6969
Now that i think about it m is usually mass... not meters or length
and you made it to college??? WELL i've seen some of the ppl that have come out of your high school so i guess it shouldn't suprise me

and you made it to college??? WELL i've seen some of the ppl that have come out of your high school so i guess it shouldn't suprise me
Hey some of us are learning to be engineers trying to get real jobs, not get paid to sit around and eat donuts all day!

19. Originally Posted by OSTIE
A nonconductor has an internal electric field that varies radially
E = 5.2 * (V/m^4) * r^3 * (r_vector)

a) Find the E force on an electron at r = .25m

b) Find the change in C from r = 0 to r = .24

c) The electron is released from rest at r = .25m, Find the speed of the electron at r = 0
Just incase anyone was dying to figure this out, lol....
It ended up being easy as FCK and I didnt get it till i tried to put the r in the equation.... since r is in meters, the bottom of the equation is m^3... cancel that with the m^4 on top and you are left with E in terms of V/m... plug that value into the equation F(e_field) = qE and theres the answer to part A. The rest is all easy after that.

20. told you...

21. good god..what ever happened to addition and subtraction???