# Two charges of  -1 C  and  -3 C are positioned on a line at points  -2  and  12 , respectively. What is the net force on a charge of  4 C at  -1 ?

Apr 30, 2017

${\vec{F}}_{B D} = 35.361 \cdot {10}^{9} N$

#### Explanation:

Upon seeing the Diagram we first focus on the FBD for the charge at D .
general formula used here is
$F = \frac{1}{4 \pi {\epsilon}_{o}} \cdot \frac{{q}_{1} \cdot {q}_{2}}{r} ^ 2$

$\therefore$ ${F}_{D B} = 9 \cdot {10}^{9} \cdot \frac{- 1 \cdot 4}{1} ^ 2 = - 36 \cdot {10}^{9} N$
Which is attractive force due negative x-axis direction .

${F}_{D C} = 9 \cdot {10}^{9} \cdot \frac{- 3 \cdot 4}{13} ^ 2 = - 0.639 \cdot {10}^{9}$
hence , ${\vec{F}}_{D B} > {\vec{F}}_{D C}$

so the direction is towards ${\vec{F}}_{D B}$
hence the net force is in the direction of ${\vec{F}}_{B D} = 35.361 \cdot {10}^{9} N$