Question

A student attaches two identical balloons (X and Y) to the ceiling using a nylon thread so that the balloons are near each other. The table shows the observations from three different activities performed with the balloons.

What evidence supports that there is a non-contact force between the balloons?
A. The balloons are not in contact and tend to move away from each other when both are rubbed with wool.
B. The balloons are not in contact and tend to move away from each other when both are rubbed with rubber.
C. The balloons are not in contact and tend to move close to each other when both are rubbed with a glass rod.
D. The balloons are not in contact and tend to move close to each other when both are rubbed with wool.

Answer 1

A.

When both balloons are rubbed with wool they acquire the same type of electric charge and repel each other even though they are not touching. That repulsion at a distance is evidence of a non‑contact (electrostatic) force. (Options C and D describe attraction despite both being rubbed the same way, which is inconsistent with like charges; B is unlikely because rubbing rubber on rubber produces little charge transfer.)