Answer
$F = 511.43 N $ or $5.1 \times 10^2 N$
Work Step by Step
Using the Coulomb force equation $F = \frac{kq^2}{r^2} $
The proton number of Helium = 2
The proton number of Thorium = 90
$r = 9.0 \times 10^{-15} m $
$F = \frac{(8.99 \times 10^9 N . m^2 / C^2)(2)(90)(1.6 \times 10^{-19}C)^2}{(9.0 \times 10^{-15} m )^2} $
$F = 511.43 N $
