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I've done this problem at least 85 times what am I doing wrong?

  • #1

Homework Statement


"Two tiny chips of plastic masses 4.5x10^-5 are separated by a distance of 1.5 mm. Suppose that they carry equal and opposite electrostatic charges +/-q. What must the magnitude of the charge be if the electric attraction between them is equal to the weight of one chip?"

Homework Equations


Fe=k*[(qxq)/d^2]
weight= mass (in kg) x 9.8 m/s^2
q=charge
d=distance
k=Coloumb's constant, 8.99x10^9


The Attempt at a Solution


1. First I have calculated the weight of one mass: .0045kg x 9.8 = .0441 N
2. then I set that equal to Coloumb's eq to try to solve for q. I divided k to the left so .0441 / 8.99x10^9 = 4.9054x10^-12.
3. I multiplied 4.9054x10^-12 by d^2 (or .0015^2) and got 1.1x10^-17
4. At this point I have q^2=1.1x10^-17 so I do a square root and get 3.322x10^-9. I have tried to tweek my answer so many times but to no more avail. I have spent almost an hour on this problem (pathetic, I know) but this problem set is due tomorrow and smartwork is being uncooperative. I would really appreciate any help!
 

Answers and Replies

  • #2
tiny-tim
Science Advisor
Homework Helper
25,832
249
welcome to pf!

hi vitaebellaa! welcome to pf! :smile:
"Two tiny chips of plastic masses 4.5x10^-5

1. First I have calculated the weight of one mass: .0045kg x 9.8 = .0441 N
shouldn't that be 0.000045 ? :redface:
 
  • #3
1,137
0
WOW!!! 85 times??? ... i have to say .. you got patience
 

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