pls help with this electrostatics frq for ap physics 2🙏

Question

Two small conducting spheres attached to very thin silk filaments hang from a very large metal beam. The silk attached to sphere 1 is dry and therefore nonconducting, while the silk attached to sphere 2 is wet, making it a conductor. Initially the spheres are uncharged. A student takes a positively charged plastic rod and moves it close to both spheres, holding the rod the same distance from each sphere as shown above. Throughout the experiment, the rod never touches the spheres, and the spheres never touch each other.

a. Which of the spheres moves toward the rod? If they both do, which one moves closer to the rod? Explain your reasoning, using words and diagrams.

The wet silk filament attached to sphere 2 gradually dries out. After the silk is completely dry, the rod is moved far away from both spheres.

b. Indicate below how the two spheres are now positioned, relative to their original vertical positions.

___ Closer to each other

___ Farther from each other

___ In their original vertical positions

Explain your reasoning.

c. Which of the following describes how the forces exerted by the spheres on each other now compare?

___ Sphere 1 exerts a greater force on sphere 2 than sphere 2 exerts on sphere 1.

___ Sphere 2 exerts a greater force on sphere 1 than sphere 1 exerts on sphere 2.

___ Sphere 1 exerts the same force on sphere 2 that sphere 2 exerts on sphere 1.

Briefly explain your reasoning.

Answer 1

a) Both spheres have zero net charge. The spheres themselves are both conductors, so electrons can easily move about it. That means that the sides of the spheres closest to the positively charged rod will be negatively charged (since opposite charges attract), and the part of the sphere furthest from the rod will be positively charged. Since those negative charges are closer, each sphere will have a net attractive force to the rod.

Sphere 2 is connected a large metal object, and sphere 1 is isolated. Since sphere 2 has a greater pool of freely moving electrons, it should be more polarized and have a stronger attraction to the rod than sphere 1 has.

b) Both spheres are now connected to the metal beam, so charges can easily move through each piece. Assuming the rod was initially placed between the spheres, both spheres start with the negative side of their polarizations facing each. Those negative charges will repel, and so the charges should redistribute themselves and the spheres should lose their polarizations and should return to their original positions

c) Without knowing anything about electromagnetism, the two forces must be equal and opposite of each other, as according to Newton's 3rd Law of Motion!