# Electrical Force Problem

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1. Apr 8, 2016

### komarxian

1. The problem statement, all variables and given/known data
An alpha particle (charge equals +2e) is sent at high speed toward a gold nucleus (charge equals +79e). What is the electrical force acting on the alpha particle when it is (2.0 x 10-14) m from the gold nucleus?

2. Relevant equations
I tried using Coulomb's law, which is E = k(q1q2/r2), with k = 9 x 109.

3. The attempt at a solution
I attempted to use Coulomb's law, and plugged it in to get

E = (9 x 109)(2e)(79e)/(2 x 10-14)

E= 2.6 x 1040
E is a repelling force

The answer in my textbook is E=91 N and it is a repelling force (I got that part right at least!), and I would really like to know where I went wrong. I was thinking maybe by some chance I plugged it into my calculator wrong, but if someone could double check or tell me where I went wrong, that would be amazing.

Thank you so much in advance.

2. Apr 8, 2016

### Staff: Mentor

In your equation e represents the fundamental unit of charge, not e the base of the natural logarithms. What's the charge on a proton?

3. Apr 8, 2016

### komarxian

OH! Thank you so much. I got the right answer. A proton is q = +1.6 x 10-19 C. Now I know that for in the future.