Question

Compute the electric force between two charges of 5×10-9 C and -3×10-8 C which are separated by r=10 cm

Answer 1

The force is given as follows:

$$F = k\dfrac{|q_1q_2|}{r^2}$$

where $k = 9\times 10^9N\cdot m^2/C^2, q_1 = 5\times 10^{-9}C,q_2 = -3\times 10^{-8}C$ and $r = 10cm = 0.1m$. Thus, obtain:

$$F = \dfrac{9\times10^9\cdot 5\times 10^{-9}\cdot 3\times 10^{-8}}{0.1^2} =1.35\times 10^{-4}N$$

Answer. $1.35\times 10^{-4}N$.