Air is contained in a rigid well-insulated tank with a volume of 0.6 m3. the tank is fitted with a paddle wheel that transfers energy to the air at a constant rate of 4 w for 1 h. the initial density of the air is 1.2 kg/m3.
if no changes in kinetic or potential energy occur, determine:

(a) the specific volume at the final state, in m^3/kg
(b) the energy transfer by work, in kj.
(c) the change in specific internal energy of the air, in kj/kg.

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?

When a bicycle coasts uphill, it moves slower and slower as it climbs. why? a. its kinetic energy is transforming into heat energy. b. its potential energy is transforming into kinetic energy. c. its kinetic energy is transforming into potential energy and heat energy. d. its potential energy is transforming into kinetic energy and heat energy.

The law of the conservation of momentum says that the total momentum of any closed and isolated system cannot