Question

An atomic nucleus has a charge of +40e. an electron is 10-9 m from the nucleus. what is the force on the electron?

Answer 1

The electron charge is equal to
`-e=-1.6\cdot 10^(-19)C`. The atomic nucleus of the problem has a charge of
`+40 e=40\cdot (1.6\cdot 10^(-19)C)=6.4\cdot 10^(-18)C`. The distance between the nucleus and the electron is
`r=10^(-9)m`, so we can calculate the electrostatic (Coulomb) force between the two:

`F=k_e ((-e)(+40e) )/(r^2) =8.99\cdot 10^9 Nm^2C^(-2) ((-1.6\cdot 10^(-19)C)(6.4\cdot 10^(-18)C))/((10^(-9)m)^2) =`

`=-9.2 \cdot 10^(-9) N`
which is attractive, since the two charges have opposite sign.