The equation for the doppler shift of a sound wave of speed v reaching a moving detector is f ? = f v + vd v ? vs , where vd is the speed of the detector, vs is the speed of the source, f is the frequency of the source, and f ? is the frequency at the detector. if the detector moves toward the source, vd is positive; if the source moves toward the detector, vs is positive. a train moving toward a detector at 29 m/s blows a 310 hz horn. what frequency is detected by a stationary train? the velocity of sound is 343 m/s.

True or false: the cycle of seasons on the earth is caused by the tilt of the earth on its axis toward and away from the sun.

Electric field of the earth. the earth has a net electric charge that causes a field at points near its surface equal to 150 n> c and directed in toward the center of the earth. (a) what magnitude and sign of charge would a 60-kg human have to acquire to overcome his or her weight by the force exerted by the earth’s electric field? (b) what would be the force of repulsion between two people each with the charge calculated in part (a) and separated by a distance of 100 m? is use of the earth’s electric field a feasible means of flight? why or why not?

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