Question

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

Answer 1

`F_"net"=28.10^9" N"`

Explanation:

`"The force between two charges is given by formula:"`

`F=k*(q_1*q_2)/r^2`

`r:"distance between two charges"`
`q_1:"the first charge"`
`q_2:"the second charge"`
`F_"AB":" represents the force between charges A and B"`
`F_"CB":"represents the force between charges C and B"`
`F_"AB" and F_"CB" " are opposite forces"`
`F_"AB"=k*((-4)*(-4))/2^2" "F_"AB"=(16*k)/4=4*k`

`F_"CB"=k*((-2)*(-4))/3^2=" "F_"AB"=(8k)/9`

`F_"net"=F_"AB"-F_"CB"`

`F_"net"=4*k-(8*k)/9`

`F_"net"=(36*k-8*k)/9`

`F_"net"=(28*k)/9" "k=9*10^9`

`F_"net"=(28*cancel(9)*10^9)/cancel(9)`

`F_"net"=28.10^9" N"`