force on charge and halfway between

Question

Two charges of +10 – 6 C are located 1 cm apart. (a) What is the force on a charge +10 – 8 C halfway between them? (b) What is the force on a charge of –10 – 8 C at the same place?

Answer 1

Force between two charges = F = K q1*q2/ r²

for half way d = 0.5 cm = 0.5*10^-2 m

q1 = 10^-6 C= q2

K= 9 * 10⁹

F₁ = 9*10⁹ *10^-6 * 10^-6 / (5*10^-3 )² N ( force of attraction as charges are of opposite signs)) = 360N

F_{2 =} 9*10⁹ *10^-6 * 10^-6/ (10^-2 )² N ( Force of attraction for distance 1cm) = 9* 10^{- 3} /( 10^-4 ) = 90N