# Homework Help: Calculate the tension in a tube

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1. Oct 30, 2014

### Quantum Fizzics

1. The problem statement, all variables and given/known data

given mass: 100g(the one hanging)
Q1 = -30(mu)C
Q2 = 70(mu)C
Q3 = 50 (mu)C
T=?
Length of tube = 2m
Length of rope = 1m
2. Relevant equations
Ft + Fg + Felect =0
F =k *q1*q3/d2

3. The attempt at a solution
Those were the equations I have done so far, so the answer is 46N & the answer I got was -45N(ref dir) but I'm not sure if I have done it right here is the diagram : http://gyazo.com/1d33f7708faf12ffea9138b7c2ee6eac
How I did it at first:
Ft (+)Fg(+)Felect(+) = 0
Ft+ 0.1(10) + 9x10^9x70x10^(-6)x50x10^-6/1
FT= -31.5N

F13 = kxq1xq3/d2
= 9x10^9(-30x10^-6)(50x10-6)/1^2
F13= +- 13.5N

2. Oct 30, 2014

### SteamKing

Staff Emeritus
It seems like you have omitted a portion of the problem statement. It's not clear what you are supposed to be doing here. Can you please post the original problem as it appeared in its original form?

3. Oct 30, 2014

### Quantum Fizzics

That was the whole question. He just gave us the diagram, & the numbers and told us to calculate the tension.

4. Oct 31, 2014

### haruspex

That doesn't seem to give a stable arrangement. Shouldn't the negative charge be in the middle?