Suppose that you want to freeze 1 kg of water for a party, and only have 5 minutes to do it. relying on nothing but your keen physical abilities, a dixicup, duct tape and a piece of string, you manage to build a refrigerator unit which can do the job. the temperature inside the refrigeration unit is 273 k, and the temperature outside is 350 k. since you are a brilliant uiuc student, assume that your refrigerator has the maximum possible efficiency. the latent heat of fusion of water is 3.33×105 j/kg assume that the initial temperature of the water is 273 k. 1) what is the heat flow ( q_ cold/time ) out of the cold well per second in j/s?

Ahowler monkey is the loudest land animal and, under some circumstances, can be heard up to a distance of 4.6 km. assume the acoustic output of a howler to be uniform in all directions and that the threshold of hearing is 1.0 × 10-12 w/m2. what is the acoustic power emitted by the howler

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?

How would a small bar magnet be oriented when placed at position x?