Question

The charges on two metallic balls are 5.0 and 7.0 coulombs respectively. They are kept 1.2 meters apart. What is the force of interaction between the two? (k = 9.0 * 10© newton·metersÆ/coulombÆ)

Answer 1

We know, F = k * q₁ * q₂ / r²

Substitute the known values, 
F = 9 * 10⁹ * 5 * 7 / (1.2)²

F = 315 * 10⁹ / 1.44

F = 218.75 * 10⁹ N

F = 2.1875 * 10¹¹ N   [ Final Answer ]

Hope this helps!