A coil is rotated in a magnetic field generating an emf given by emf = NBA? sin ?, where ? = ?t. At which angle ? is the emf one-third of its maximum value?
a. 0°
b. 19.5°
c. 6.4°
d. 70.5°
e. 60.0º
b
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What does enriching uranium do?
a. Increases the percentage of radioactive uranium-235 and thus improves the probability of chain reactions. b. Increases the percentage of uranium-238 and thus improves the probability of chain reactions. c. Increases the fraction of the material that consists of plutonium. d. Increases the percentage of neutrons in the bombardment beam that attempts to set off a chain reaction. e. Increases the speed at which uranium decays into lead, i.e., decreases the half-life.
Can an element decay "backward" in the periodic table, to a lower atomic number?
A) No, in fact elements cannot alter their atomic number by radioactive decay. B) No, but an element can decay to a higher atomic number. C) Yes, by beta decay. D) Yes, by alpha decay. E) Yes, radioactive decay always causes elements to decay to a lower atomic number.
A 0.20-km wide river has a uniform flow speed of 4.0 m/s toward the east. It takes 20 s for a boat to cross the river to a point directly north of its departure point on the south bank. In what direction must the boat be pointed in order to accomplish this?
a. 23° west of north b. 20° west of north c. 24° west of north d. 22° west of north e. 17° west of north
Plane polarized light of intensity 
is sent through a polarizer rotated 45
clockwise to the original plane of polarization and then through a second polarizer rotated 45 
counter-clockwise measured from the original plane of polarization. What is the transmitted intensity?
A. 0.71 
B. 0.50
C. 0.35
D. 0.25
E. 0