Calculating Electrical Force on Alpha Particle Near Gold Nucleus

[komarxian]

Homework Statement

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?

Homework Equations

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

The Attempt at a Solution

I attempted to use Coulomb's law, and plugged it into get

E = (9 x 10⁹)(2e)(79e)/(2 x 10^-14)

and my answer was

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.

 

[gneill]

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?

 

[komarxian]

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?

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.