Can anyone help me with this: 1. Consider two different car engines, Engine A and Engine B. What type of energy is useful for a car?

Engine A gives off 70% thermal energy, What is its maximum efficiency?

Engine B has maximum efficiency of 25%. Which car probably gets better gas mileage, A or B? Explain.

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