# Homework Help: Electrostatics Questions

1. Jan 24, 2006

### music_man05

Answers or Steps, or even formulas are welcome, Any answer to any of them!
Okay First qusetion...

A proton is placed in an electrical field that counters the effect of gravity at sea level. Find The Electric Field.

Second Question...

A Proton is accelerated from rest in an electric field of 500.0 N/C. Find the velocity and kinetic energy of the proton at 3.00x10^-5s.

And Last Problem....

Three +1.00 uC charges are placed in the corners of a rectangle. height 2cm and width 10cm. Find the electric field at the forth unoccupied corner.

Last edited: Jan 24, 2006
2. Jan 24, 2006

### StatusX

Any ideas? You have to at least show an attempt to do the problems before you'll get any help.

3. Jan 24, 2006

### music_man05

OK here is where I am at

For the first question All I can think of is the formula Fg = Fq then mg=qE then E = mg/q and q = 1e is that correct??

For the second one I have just KE = 1/2mv^2 E = 500N/C E = Fe/q = Kq/r^2

and for the third one I have Nothing, I don't even know where to start...Maybe I just need a starter for it or give me a formula

4. Jan 24, 2006

### StatusX

\begin{align*} \vec E &= \frac{k q}{|r|^2} \hat r \\ &= \frac{k q}{|r|^3} \vec r\end{align*}
\begin{align*} E_x &= \frac{k q}{|r|^3} r_x \\ &= \frac{k q}{(\Delta x^2+\Delta y^2)^{3/2}} \Delta x \end{align*}