Question

14 ot 14 en a charged balloon sticks to a wall, the downward gravitational force is balanced by an upward static friction force. The normal force is provided by the electrical attraction betweer charged balloon and the equal but oppositely charged polarization induced in the wall's molecules. Rev Part A and the average distance between the opposite charges is o.85 mm, what minimum amount of If the mass of a balloon is 1.9 g, its coefficient of static friction with the wall is 0.75, charge must be placed on the balloon in order for it to stick to the wall? Express your answer to two significant figures and include appropriate units. alue Units Provide Feedback Return to Assignment

Answer 1

Mass of balloon (m) = 1.9 times 10^-3 kg Coefficient of static friction (mu) = 0.75 Average distance between charges = 0.85 times 10^-3 m To stick the balloon without falling down, f_s = mg where f_s = mu_s N N rightarrow Normal reaction between wall and balloon surfaces Here Normal reaction is provided by electrostatic attraction between charges on balloon and wall. i.e N = 1/4 pi epsilon_0 q^2/r^2 mu_s N = mg mu_s times 1/4 pi epsilon_0 q^2/r^2 = mg q^2 = mg r^2 times 4 pi epsilon_0/mu_s = 1.9 times 10^-3 times 9.8 times (0.85 times 10^-3)^2/0.75 times 9 times 10^9 = 1.9 times 9.8 times 0.85 times 0.85/0.75 times 9 times 10^-9/10^9 = 1.993 times (10^-9)^2 q = squareroot 1.993 times (10^-9)^2 = 1.41 times 10^-9 C q = 1.41 nC