# Physics grd 12 alpha particles, have no idea what I'm even doing please help?

I'm completely lost studying in a test, I try to follow along in class and I fall behind writing down what I don't understand. Anyways here's the question, maybe I'll understand some of the other questions if I get this one.. Ernest Rutherford used alpha particles (charge +2e) and thin gold foil to probe the structure of the atom. Given that the nucleus of a gold atom has 79 protons, calculate the electrostatic repulsive force between the alpha particle and the gold nucleus when the seperation distance between the two is 6.2 x 10^-14 m.

### 1 Answer

- NCSLv 73 weeks agoFavorite Answer
This is a straightforward application of the Coulomb force:

F = kQq / d²

where k = 1/4πε₀ = 8.99e9N·m²/C²

so

F = 8.99e9N·m²/C² * (2*1.6e-19C) * (79*1.6e-19C) / (6.2e-14m)²

F = 9.5 N

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so that's a constant?