Adj starts up her phonograph player. the turntable accelerates uniformly from rest, and takes t1 = 11.9 seconds to get up to its full speed of f1 = 78 revolutions per minute.

case 2: the dj then changes the speed of the turntable from f1 = 78 to f2 = 120 revolutions per minute. she notices that the turntable rotates exactly n2= 11 times while accelerating uniformly.

t1 = 11.9 seconds
n2 = 11 times

part (a) calculate the angular speed of the turntable while it is turning at f1 = 78 in radians/second in case 1.

part (b) how many revolutions does the turntable make while accelerating in case 1?
part (c) calculate the magnitude of the angular acceleration of the turntable in case 1, in radians/second2.
part (d) calculate the magnitude of the angular acceleration of the turntable (in radians/second2) while increasing to 120 rpm (case 2).
part (e) how long (in seconds) does it take for the turntable to go from f1 = 78 to f2 = 120 rpm?

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?

What are the necessary conditions for fusion?

Acapacitor is storing energy of 3 joules with a voltage of 50 volts across its terminals. a second identical capacitor of the same value is storing energy of 1 joule. what is the voltage across the terminals of the second capacitor?