(adsbygoogle = window.adsbygoogle || []).push({}); 1. The problem statement, all variables and given/known data

Three small spheres are placed at fixed points along the x-axis, whose positive direction points towards the right.

Sphere A is at x = 46.0 cm, with a charge of –6.00 μC.

Sphere B is at x = 55.0 cm, with a charge of 6.00 μC.

Sphere C is at x = 59.0 cm, with a charge of –7.00 μC.

(a)Calculate the magnitude of the electrostatic force on sphere B.

(b)What would be the magnitude of the electric field at the point where sphere B was located?

2. Relevant equations

Coulomb's law [tex]\vec{F_{1,2}}= k_e \frac{q_1q_2}{r^2}[/tex]

electric field: [tex]\vec{E}=\frac{\vec{F_e}}{q_0}[/tex]

[tex]\vec{E}= k_e \frac{q}{r^2}[/tex]

3. The attempt at a solution

For part(a), I have used Coulomb's law as follows:

[tex]\vec{F_{A,B}}= (8.9 \times 10^9) \frac{(6 \times 10^{-6} C) (6 \times 10^{-6} C)}{9^2}[/tex]

= 3.95 x 10^{-3}N

[tex]\vec{F_{C,B}}= (8.9 \times 10^9) \frac{(7 \times 10^{-6} C) (6 \times 10^{-6} C)}{4^2}[/tex]

= 0.02336 N

Taking F_{A,B}as negative and F_{C,B}to be positive:

0.02336 - 3.95 x 10^{-3}N = 0.0194 N

But the answer must be 196 N. What's wrong?

(b)I tried the 3rd equation equation above but it didn't work...

[tex](8.9 \times 10^9) \frac{196}{9^2} = 2.15 \times 10^{10}[/tex]

Again this is wrong. It must be 32700000 N/C. Any help with this problem is appreciated.

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# Homework Help: Charged spheres

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