Two balloons filled with air are tied to very light 0.5-m-long string. The loose ends of the strings are taped to the same position on a horizontal bar. When both are equally rubbed with the same material they both develop a static charge and repel each other making an angle of 30 with respect to the vertical. (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 excess charges on each balloon. Clearly state any assumptions made in your estimation. (d) If a small 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 calculation