The strongest lines present in spectral class A stars are absorption lines of
A) complex molecules.
B) hydrogen.
C) oxygen.
D) iron.
E) helium.
B
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A vertical wire carries a current straight up in a region where the magnetic field vector points due North. What is the direction of the resulting force on this current?
A) North B) downward C) East D) West E) South
Good tracers of the spiral arms of our galaxy are all I. very old. II. very young. III. very luminous. IV. moving with large radial velocities
a. I & III b. I & IV c. II & III d. II & IV e. I, III, & IV
Light from an astronomical source is found to be shifted to a one percent lower frequency than had the source been at rest. What radial velocity could cause such a shift?
A. 
m/s moving away from the observer
B. 
m/s moving away from the observer
C. 
m/s moving toward the observer
D. 
m/s moving toward the observer
E. 
m/s moving away from the observer
A monel shell (Em 5 170 GPa, d3 5 12 mm, d2 5 8 mm) encloses a brass core (Eb 5 96 GPa, d1 5 6 mm). Initially, both shell and core are a length of 100 mm. A load P is applied to both shell and core through a cap plate. The load P required to compress both shell and core by 0.10 mm is approximately:
(A) 10.2 kN
(B) 13.4 kN
(C) 18.5 kN
(D) 21.0 kN