Find the attractive Coulombic force

Question

 A proton is located at x =1.0nm, y=0.0nm and an electron is located at x=0.0nm, y=4.0nm.

Find the attractive Coulombic force between them. (k= 9x10^9Nm^2/C^2)

Answer 1

First, find the distance between the particles. This is the hypotenuse of a triangle with sides 1 nm and 4 nm and it equals sqrt(1² + 4²) = 4.1 nm = 4.1 x 10^-9 m. Use the charge on electrons = -1.6 x 10^-19 C and protons = 1.6 x 10^-19 C and k = 9 x 10⁹ Nm²/C².

F = kq₁q₂ / d² = (9 x 10⁹)(-1.6 x 10^-19)(1.6 x 10^-19) / (4.1 x 10^-9)² = -1.4 x 10^-11 N

The minus sign shows the force is attraction between the particles.