# Two charges of  -1 C  and  -8 C are positioned on a line at points  6  and  -4 , respectively. What is the net force on a charge of  -3 C at  1 ?

Oct 14, 2016

#### Answer:

$\approx 7.6 \times {10}^{9} N$

#### Explanation:

You have not provided units for the distances , so they have been assumed to be in metres in the solution provided....in blue.

Always draw it first.

The force between 2 charges follows Coulomb's Law

$F = k \frac{{q}_{1} {q}_{2}}{r} ^ 2$ where k is Coulomb's constant $k = 9 \times {10}^{9} N {m}^{2} {C}^{- 2}$

In this case both forces on the -3C charge are repulsive forces as indicated by the green arrows

The net force, acting left to right is:

${F}_{\text{net}} = \frac{k}{{\textcolor{b l u e}{5}}^{2}} \left(\left(- 8 \cdot - 3\right) - \left(- 1 \cdot - 3\right)\right)$

${F}_{\text{net}} = \frac{21 k}{25} \approx 7.6 \times {10}^{9} N$