# What is the electrical force of attraction between two balloons with separate charges of +3.5 x 10-8 C and -2.9 x 10-8 C when separated a distance of 0.65 m?

Feb 20, 2015

The answer is: $F = - 2 , 16 \times {10}^{-} 5 N$.

The law is:

$F = \frac{1}{4 \pi {\epsilon}_{0}} \frac{{q}_{1} {q}_{2}}{r} ^ 2$, or $F = {k}_{e} \frac{{q}_{1} {q}_{2}}{r} ^ 2$, where

${k}_{e} = 8 , 98 \cdot {10}^{9} {C}^{-} 2 {m}^{2} N$ is the constant of Coulomb.

So:

$F = 8 , 98 \times {10}^{9} {C}^{-} 2 {m}^{2} N \cdot \frac{3 , 5 \times {10}^{-} 8 C \cdot \left(- 2 , 9\right) \times {10}^{-} 8 C}{0 , 65 m} ^ 2 =$

$= - 216 \times {10}^{-} 7 N = - 2 , 16 \times {10}^{-} 5 N$.

A very detailed explanation of Coulomb's law is here: http://socratic.org/questions/what-is-the-electrical-force-of-attraction-between-two-balloons-with-separate-ch