Two balloons filled with air are tied to very light strings and the loose ends o
ID: 2109689 • Letter: T
Question
Two balloons filled with air are tied to very light strings and the loose ends of the strings are taped to the same point on a horizontal bar. When both are equally rubbed with the same material they both develop a static charge and repel each other.
A) With this experiment alone can you tell what type of charge is on the balloon? Explain
B) Is this a stable or unstable equilibrium?
C) Estimate the number of of excess charges on each balloon. Clearly state any assumptions made in your estimation.
D) If a charged sphere is placed in the middle of the two balloons and the angle between them doubles, estimate the number of excess charges on the sphere, again being sure to state any assumptions used in your calculations.
Explanation / Answer
a). The balloons, having a greater attraction for electrons than the material they are rubbed with, would acquire a negative charge. The balloons would have the same type of charge and they would subsequently repel each other. b). Unstable equilibrium c).It is assumed that the balloons have the same quantity of charge since they are charged in the same manner. Since Q1 is equal to Q2, the equation can be rewritten as F = kQ^2/d^2 ; d is the distance between balloons. Q = sqrt(F*d^2/k) d). Let the initial angle b/w the balloons be theta. Now, if the angle b/w the balloons doubles, the distance b/w them will be 2d*cos(theta). F = kQ^2/[2d*cos(theta)]^2 ; [2d*cos(theta)] is the distance between balloons. Q = sqrt[4F*d^2*cos^2(theta)/k]