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Hey guys I'm from Brazil and I'm studying physics to pass in one of the best universities here. However, the physics test is much harder than what we study at school. I am currently working on a book called "Selected Elementary Physics", by MIR Moscou, and I am having a lot of trouble. I don't have anyone who can help me solve these problems, and I am hoping these forums would be a good solution to my problem. I'm from Brazil and my english terminology on Physics is very bad, and I might make bad translations, which I will point out by (?)(?). I'll start with a first one, hoping that it somebody can solve.

Two equal (?)"Charges"(?) [tex]+Q[/tex] are fixed and located at a distance [tex]a[/tex] from each other. Along the simmetry axis of these charges, a third charge, [tex]-q[/tex], can be moved, which has a mass [tex]m[/tex]. Considering the distance from the [tex]-q[/tex] particle to the line that unites the [tex]+Q[/tex] charges, determine the (?)oscillations period(?) of the [tex]-q[/tex] charge.

[tex]F\,=\,\frac{1}{4\pi\epsilon}\,.\,\frac{Q\,.\,q}{d^2}[/tex]

Since it says the distance is small, I assumed it to be infinetely small, and considered the distance from [tex]+Q[/tex] to [tex]-q[/tex] to be [tex]a[/tex] as well. I then used [tex]F\,=\,m.a[/tex], with no effect. I don't know how to approach this problem, any help is appreciated.

Answer: [tex]\Large{T\,=\,\pia\,\sqrt{\frac{\pi\epsilon _o.m.a}{Qq}}\,.\pi\,.\,a}[/tex]

**1. Homework Statement**Two equal (?)"Charges"(?) [tex]+Q[/tex] are fixed and located at a distance [tex]a[/tex] from each other. Along the simmetry axis of these charges, a third charge, [tex]-q[/tex], can be moved, which has a mass [tex]m[/tex]. Considering the distance from the [tex]-q[/tex] particle to the line that unites the [tex]+Q[/tex] charges, determine the (?)oscillations period(?) of the [tex]-q[/tex] charge.

**2. Homework Equations**[tex]F\,=\,\frac{1}{4\pi\epsilon}\,.\,\frac{Q\,.\,q}{d^2}[/tex]

**3. The Attempt at a Solution**Since it says the distance is small, I assumed it to be infinetely small, and considered the distance from [tex]+Q[/tex] to [tex]-q[/tex] to be [tex]a[/tex] as well. I then used [tex]F\,=\,m.a[/tex], with no effect. I don't know how to approach this problem, any help is appreciated.

Answer: [tex]\Large{T\,=\,\pia\,\sqrt{\frac{\pi\epsilon _o.m.a}{Qq}}\,.\pi\,.\,a}[/tex]

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