The position vectors of two point charges of 2 nC each are `(2hati + 3hatj - hatk)`m and `(3hati + 5hatj + hatk)`m respectively. Magnitude of the coulombian force acting between them is........

Options

A. `4 xx 10^(-3)` N
B. `4 xx 10^(-9)` N
C. `4 xx 10^(-6)` N
D. `10^(-3)` N

Answer

A

Explanation

`vecr = vecr_(2) -vecr_(1) = (3hati + 5hatj + hatk) -2(hati - 3hatj -hatk)`
`=(hati + 2hatj + 2hatk)`
`therefore r = sqrt(1+4+4) = 3m`
`therefore F = (kq^(2))/r^(2) = (9 xx 10^(9) xx 4 xx 10^(-12))/9`
`=4 xx 10^(-3)` N