The cosmic microwave background radiation was emitted during a time when ____ was the important process in the Universe
a. recombination
b. ionization
c. fusion
d. antiproton production
e. positron production
a
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An organ pipe is 60.0 cm long and is open at one end and closed at the other. The frequency of the third mode is 300 Hz higher than the frequency of the second mode. What is the velocity of sound?
A. 280 m/s B. 300 m/s C. 320 m/s D. 340 m/s E. 360 m/s
An aluminum cantilever beam (E 5 72 GPa) with a square cross sec-tion and span length L 5 2.5 m is subjected to uniform load q 5 1.5 kN/m. The allowable bending stress is 55 MPa. The maximum deflection of the beam is approximately:
(A) 10 mm
(B) 20 mm
(C) 30 mm
(D) 40 mm
Suppose you sound a 1056-Hz tuning fork when you strike a note on the piano and hear 2 beats/second. You tighten the piano string very slightly and now hear 3 beats/second. What is the frequency of the piano string?
A) 1053 Hz B) 1054 Hz C) 1056 Hz D) 1058 Hz E) 1059 Hz
What is the purpose of adding aluminum salts and a base to water during water treatment?
A) The two together gel and trap dirt and bacteria. B) The higher pH kills bacteria. C) The aluminum removes the rust taste from the water. D) The base dissolves the dirt. E) It improves the taste.