Answer:
F = 91.27 N
Step-by-step explanation:
Parameters given:
Charge of alpha particle, q = +2.0e =
=

Charge of gold nucleus, Q = +79e =
=

Distance between the alpha particle and gold nucleus, r =

Electric force is given as:
F =

where k = Coulomb's constant
Therefore:

The electric force acting on the alpha particle when the alpha particle is
from the gold nucleus is 91.27 N.