Question

A charge of `-2 C` is at `(4, 7)` and a charge of `-1 C` is at `( 5, 2)`. If both coordinates are in meters, what is the force between the charges?

Answer 1

Charge `q_1=-2C` is placed at `(4,7)`
Charge `q_2=-1C` is placed at `(5,2)`

Distance between both charges is
`r=sqrt((5-4)^2+(2-7)^2`
`r=sqrt((1)^2+(-5)^2`
`r=sqrt(1+25`
`r=sqrt(26) m` and `r^2=26`

Force between two charges `q_1` and `q_2` is
`F=(kq_1q_2)/r^2` where `k=9*10^9 Nm^2/C^2`
`=>F=((9*10^9)(-2)(-1))/(26`
`=>F=((9*10^9)(2))/(26`
`=>F=((9*10^9))/(13) N`
`=>F=0.6923*10^9 N`
or
`=>F=6.923*10^8 N`