¡Hola!
Si :
1 μC = 0, 000001 C
1 nC = 0, 000000001 C
Entonces :
5μC = 0, 000005 C = ><img src="https://tex.z-dn.net/?f=5%2A10%5E%7B-6%7D%5C%3A%20C" />
7 nC = 0, 000000007 C = ><img src="https://tex.z-dn.net/?f=7%2A10%5E%7B-9%7D%5C%3AC" />
Ahora, tenemos los siguientes datos :
F (fuerza de interacción electrica) = ?
(en N)
k (constante electrostática) = <img src="https://tex.z-dn.net/?f=9%2A10%5E9%5C%3AN%2Am%5E2%2AC%5E%7B-2%7D" />
q1 (Carga Puntual) = <img src="https://tex.z-dn.net/?f=5%2A10%5E%7B-6%7D%5C%3AC" />
q2 (carga pontual) = <img src="https://tex.z-dn.net/?f=7%2A10%5E%7B-9%7D%5C%3AC" />
d (distancia de la carga fuente) = 3, 5 cm→ 0, 035 m
<img src="https://tex.z-dn.net/?f=F%20%3D%20k%2A%20%5Cdfrac%7Bq_1%2Aq_2%7D%7Bd%5E2%7D%20" />
<img src="https://tex.z-dn.net/?f=F%20%3D%209%2A10%5E9%2A%20%5Cdfrac%7B5%2A10%5E%7B-6%7D%2A7%2A10%5E%7B-9%7D%7D%7B0%2C035%5E2%7D%20" />
<img src="https://tex.z-dn.net/?f=F%20%3D%209%2A10%5E9%2A%20%5Cdfrac%7B35%2A10%5E%7B-15%7D%7D%7B0%2C001225%7D" />
<img src="https://tex.z-dn.net/?f=F%20%3D%20%5Cdfrac%7B3%2C15%2A10%5E%7B-4%7D%7D%7B0%2C001225%7D" />
<img src="https://tex.z-dn.net/?f=F%20%3D%20%5Cdfrac%7B3%2C15%2A10%5E%7B-4%7D%7D%7B1%2C225%2A10%5E-3%7D" />
[img = 10]
[img = 11]
[img = 12]
¡Espero haberte ayudado, saludos.
DexteR!