Five point charges, each of value +q are placed on five vertices of a regular hexagon of side Lm. What is the magnitude of the force on a point charge of value -q coulomb placed at the centre of the hexagon?

Explanation

If there had been a sixth charge =q at the remaining vertex of hexagon force du to tall the six charges on -q at O will be zero (as the forces due to individual charges will balance each other).
i.e. `vecF_(R)=0`

Now if `vecf` is the force due to sixth charge and `vecF` due to remaining five charges, `vecF=vecf=0`
i.e. `vecF=-vecf` or
`F=f=(1/(4 pi epsilon_(0)) (qxxq)/(L^(2)))=1/(4 pi epsilon_(0)) [q/L]^(2)`