If there is an electric force of 5 newtons between two charged particles (q1 = +10 c and q2 = +10 c), how far apart are the particles?

Using the Coulumb law,

Force (electric) = [k * Q1 * Q2] / d², "d" is "how far apart are the particles"...

F = 5 N 

Q1 = 10 C 

Q2 = 10 C 

5 = k*(10)² / d² 

5*d² = 100*k
d² = 20*k 

k is the Coulomb's constant : 9*10^9 Nm²/C²

d² = 20*(9*10^9)
d² = 18*10^10 

d = 4.2*10^5 m or 420 km 

Ihope you get it right bro