Question

force at a distance a force is a push or a pull. forces occur when objects interact. there are two groups of forces: contact forces and forces - at - a - distance. contact forces are forces that result when two interacting objects are in physical contact with each other. examples include friction, air resistance, and applied forces. forces - at - a - distance are forces that result even when the two objects are not in physical contact with each other, yet are able to exert a push or pull despite their physical separation. examples of action - at - a - distance forces include gravity, magnetism, and electromagnetics. during induction, a positively charged rod is brought near to but not touching the electroscope. the presence of the charged object above the plate of the electroscope induces charges to move up towards the conduction plate, giving the gold leaves an overall positive charge. the positive leaves repel. describe the force(s) at work. a like charges repel; force - at - a - distance b opposites attract, contact force, followed by like charges repel, contact force. c opposites attract, force - at - a - distance, followed by like charges repel, contact force. d opposites attract, force - at - a - distance, followed by like charges repel, force - at - a - distance

Explanation:

First, the positively charged rod and the neutral electroscope interact without contact, so this is a force-at-a-distance (electrostatic) force where opposite charges attract (the rod attracts negative charges in the electroscope to the top plate). Then, the gold leaves, now with an overall positive charge (like charges), repel each other; this repulsion between the leaves is a contact force as they physically touch when repelling.

Answer:

B. Opposites attract, contact force, followed by like charges repel, contact force.