Question

I am so very lost. Can Someone help me solve this?
A test charge of -5.0 x 10-7 C is placed between other charges so that it is 50 mm from a charge of -3.0 x 10-7 C and 10 cm from a charge of -6.0 x 10-7 C. The three charges lie along a straight line. The answer is 0.27N to the right. Idk how to get that?

Answer 1

So you know coulomb's law, \(F=k\dfrac{q_1q_2}{r^2}\)?

Answer 2

it's 5mm though.

Answer 3

it says 50 mm which is 5 cm

Answer 4

oh. Okay. I tried using that formula, I wrote Fnet = f1 + f2 and then tried solving for both, but I didn't get the right answer

Answer 5

yeah, that should be right. Did you use SI units, i.e. convert distance to meters?

Answer 6

Yes.

Answer 7

hm gimme me a second, i'm going to try it

Answer 8

i got 0.2696265 N which is 0.27 N

I think the problem you're having the signs

it should look like this (notice one is positive and one negative)

\(\large F=kq_1[\dfrac{q_2}{r^2}+-\dfrac{q_3}{r^2}]\)

because both charges are putting a repulsive force on the test charge (all are negative)

Answer 9

How do you know that one is negative and not both?

Answer 10

because of the signs of the charges and their interaction - all are negative, so they are repelling on another

Along the axis, each one is exerting a force, this is a vector and thus according to the axis is set it up they are opposing forces

Answer 11

Okay, I understand how they interact. I'm just uncertain how you would determine what the charge is. Sorry

Answer 12

it's given in the question -5.0 x 10-7 C

notice the negative sign, that is the sign of the chargw

Answer 13

Oh, my physics teacher told me that it wasn't

Answer 14

Thank you so much for the help. Things are so much clearer now.

Answer 15

no problem! glad i could be of assistance