Balls and rods set up to represent a solar system a set of organs and structures that provide digestion in the human body
the defense plan of a football team drawn on a whiteboard
Which option correctly identifies each description?

I. system
II. model
III. systemI. system, , II. model, , III. system , ,

I. model
II. model
III. systemI. model, , II. model, , III. system , ,

I. model
II. system
III. model
, I. model, , II. system, , III. model

I. system
II. system
III. model

Consider a uniformly charged ring in the xy plane, centered at the origin. the ring has radius a and positive charge qdistributed evenly along its circumference. a)what is the direction of the electric field at any point on the z axis? . b)what is the magnitude of the electric field along the positive z axis? use k in your answer, where k=14πϵ0. d)the ball will oscillate along the z axis between z=d and z=−d in simple harmonic motion. what will be the angular frequency ω of these oscillations? use the approximation d≪a to simplify your calculation; that is, assume that d2+a2≈a2. express your answer in terms of given charges, dimensions, and constants