Which of the following is a limitation of models? A.
Sometimes models provide data when data cannot be acquired from natural objects or events.
B.
Models usually do not have exactly the same features as the objects or events that they represent.
C.
Models are often safer to study than the objects or events that they represent.
D.
It is often easier to study models rather than the objects or events that they represent.

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