Calculate the ratio of the electrostatic force to the gravitational force between two electrons.(adsbygoogle = window.adsbygoogle || []).push({});

My effort:

[tex]

\begin{array}{l}

\frac{{\left( {\frac{{kq_{electron}^2 }}{{r^2 }}} \right)}}{{\left( {\frac{{GM_{electron}^2 }}{{r^2 }}} \right)}} \Rightarrow \\

\\

\frac{{kq_{electron}^2 }}{{GM_{electron}^2 }} = \frac{{8.988 \times 10^9 Nm^2 C^{ - 2} \times \left( { - 1.60217653 \times 10^{ - 19} C} \right)^2 }}{{6.97 \times 10^{ - 11} Nm^2 kg^{ - 2} \times \left( {9.10953826 \times 10^{ - 31} kg} \right)^2 }} = 3.9889 \times 10^{42} \\

\end{array}

[/tex]

Sorry for small tex. This should be better:

My units cancel nicely, so I assume I did it right. However, the book doesn't give the formula I used: F=kqq/r^2

It gives

[tex]

F = Q\left( {E + v \times B} \right)

[/tex]

Most text books give you the formulas you need to do the questions at the end of the chapter. So I figure I'd double check here.

In Wikipedia I looked up the mass and charge of the electron. It gave

9.109 3826(16) × 10^{−31}kg

−1.602 176 53(14) × 10^{−19}C

What do the (16) and (14) in these numbers mean?

*** Edit

I'm seeing an answer of 10^36 on

http://en.wikipedia.org/wiki/Fundamental_force

and 10^39 on

http://public.lanl.gov/alp/plasma/EM_forces.html

So I'm a bit less confident about my answer now.

**Physics Forums | Science Articles, Homework Help, Discussion**

Join Physics Forums Today!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

# Homework Help: Charge vs. gravity

**Physics Forums | Science Articles, Homework Help, Discussion**