Which diagram best shows the perceived sound wave heard by a woman after a police car has passed her?

An illustration of a person listening to the siren of a passing police car. There are circles spreading out from the siren with the wavelength close together in the front and farther apart in the back.
An illustration of a person listening to the siren of a passing police car. There are circles spreading out from the siren with the wavelength longer closer to the siren and closer together the farther from the siren on both sides.
An illustration of a person listening to the siren of a passing police car. There are circles spreading out from the siren that are concentric and evenly spaced.
An illustration of a person listening to the siren of a passing police car. There are circles spreading out from the siren with the wavelength changing in all directions.

Search coils and credit cards. one practical way to measure magnetic field strength uses a small, closely wound coil called a search coil. the coil is initially held with its plane perpendicular to a magnetic field. the coil is then either quickly rotated a quarter-turn about a diameter or quickly pulled out of the field. (a) derive the equation relating the total charge q that flows through a search coil to the magnetic-field magnitude b. the search coil has n turns, each with area a, and the flux through the coil is decreased from its initial maximum value to zero in a time ∆t. the resistance of the coil is r, and the total charge is q = i∆t, where i is the average current induced by the change in flux. (b) in a credit card reader, the magnetic strip on the back of a credit card is rapidly “swiped” past a coil within the reader. explain, using the same ideas that underlie the operation of a search coil, how the reader can decode the information stored in the pattern of magnetization on the strip. (c) is it necessary that the credit card be “swiped” through the reader at exactly the right speed? why or why not?

(a) assume the equation x = at^3 + bt describes the motion of a particular object, with x having the dimension of length and t having the dimension of time. determine the dimensions of the constants a and b. (use the following as necessary: l and t, where l is the unit of length and t is the unit of time.) (b) determine the dimensions of the derivative dx/dt = 3at^2 + b. (use the following as necessary: l and t, where l is the unit of length and t is the unit of time.)

What is the speed vfinal of the electron when it is 10.0 cm from charge 1?