Bobby hangs two inflated balloons from 2-meter strings so that they touch. He then holds the balloons apart and rubs each balloon 5 times with animal fur. He then releases the balloons. The balloons now hang a small distance apart from one another:

Question

The next step in Bobby's procedure is to touch the balloons with a metal rod and allow them to settle, and then to rub them 10 times with animal fur. Which result should he expect, and why?

(1 point)
Responses

The balloons will hang at the same elevation, because electrical repulsion is an unvarying phenomenon which results from the existence of charge and not its quantity.
The balloons will hang at the same elevation, because electrical repulsion is an unvarying phenomenon which results from the existence of charge and not its quantity.

The balloons will hang at a greater elevation, because they will have greater charges so the force of electrical repulsion between them will be greater.
The balloons will hang at a greater elevation, because they will have greater charges so the force of electrical repulsion between them will be greater.

The balloons will hang at a smaller elevation, because more thoroughly rubbing them will more completely remove their charges, reducing the electrical repulsion between them.
The balloons will hang at a smaller elevation, because more thoroughly rubbing them will more completely remove their charges, reducing the electrical repulsion between them.

The balloons will hang straight down or more closely together, because a larger number of rubs with fur will give them opposite rather than like electrical charges

Answer 1

The correct response is:

The balloons will hang straight down or more closely together, because a larger number of rubs with fur will give them opposite rather than like electrical charges.

This is because rubbing the balloons with animal fur transfers electrons between the two materials, generally resulting in the balloons becoming charged. If they were previously like-charged (both positive or both negative) after being rubbed, they would repel each other and hang apart. However, if the balloons are rubbed again and become oppositely charged (one positive and one negative) due to the increased rubbing, they will attract each other, causing them to hang closer together.