1) Charge: [tex]7.5\cdot 10^{-8} C[/tex]
Explanation:
The electrostatic force between the two shirts is:
[tex]F=k\frac{q_1 q_2}{r^2}[/tex]
where
k is the Coulomb's constant
q1 = q2 = q is the charge of each shirt (they are equally charged)
r = 4 cm = 0.04 m is the distance between the shirts
F = 0.5 N is the force
Re-arranging the equation, we can find q, the charge of each shirt:
[tex]q=\sqrt{\frac{Fr^2}{k}}=\sqrt{\frac{(0.5 N)(0.01 m)^2}{9\cdot 10^9}}=7.5\cdot 10^{-8} C[/tex]
2) Force if they are separated by 4 cm: 0.03 N
In this case, the force between the two shirts would be:
[tex]F=k\frac{q_1 q_2}{r^2}=(9\cdot 10^9)\frac{(7.5\cdot 10^{-8}C)^2}{(0.04 m)^2}=0.03 N[/tex]
