A 2.00-gram air inflated balloon is given an excess negative charge, q1 = -3.25 × 10-8 C, by rubbing it with a blanket. It is fo
und that a charged rod can be held above the balloon at a distance of d = 5.00 cm to make the balloon float. In order for this to occur, what polarity of charge must the rod possess? How much charge, q2, does the rod have? Assume the balloon and rod to be point charges. The Coulomb force constant is 1/(4π ε0) = 8.99 × 109 N·m2/C2 and the acceleration due to gravity g = 9.81 m/s2.
The rod`s charge must be positive, because the gravity force is pointing downwards and the electrostatic force must be pointing upwards (in order to balance the gravity force)
The charge is q_2 = 1.667 times 10^(-7) C
Explanation:
F_e = F_g
where F_g = m g and F_e= (1/4 pi e_0)*(q_1*q_2)/d^2,
