Animals in cold climates often depend on two layers of insulation: a layer of body fat (of thermal conductivity 0.200 w/( m k ) surrounded by a layer of air trapped inside fur or down. we can model a black bear (ursus americanus) as a sphere 1.60 m in diameter having a layer of fat 3.90 cm thick. (actually, the thickness varies with the season, but we are interested in hibernation, when the fat layer is thickest.) in studies of bear hibernation, it was found that the outer surface layer of the fur is at 2.60 c during hibernation, while the inner surface of the fat layer is at 31.2°c te °c submit request answer assume the surface area of each layer is the same and given by the surface area of the spherical model constructed for the black bear. also, assume a steady state of the heat current through the layers. part a. what should the temperature at the fat-inner fur boundary be so that the bear , part b how thick should the air layer (contained within the fur) be so that the bear loses heat at a rate of 52.0 w? loses heat at a rate of 52.0 w?

Ahypothesis is? close agreement by competent observers of observations of the same phenomena. a guess that has been tested over and over again and always found to be true. an educated guess that has yet to be proven by experiment. the long side of a right triangle. a synthesis of a large collection of information that includes guesses.

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?

Along the line connecting the two charges, at what distance from the charge q1 is the total electric field from the two charges zero? express your answer in terms of some or all of the variables s, q1, q2 and k =14ï€ïµ0. if your answer is difficult to enter, consider simplifying it, as it can be made relatively simple with some work.