A very loud train whistle has an acoustic power output of 80 W. If the sound energy spreads out spherically, what is the intensity level in dB at a distance of 100 meters from the train? (I0 = 10-12 W/m2)
a. 78.3 dB
c. 92.8 dB
b. 88.0 dB
d. 95.0 dB
B
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The sunspot cycle affects ____________. I. the latitude at which most sunspots occur II. the number of sunspots that are visible. III. the rotation rate of the sun's equator IV. the magnetic polarity of the sunspot pair members in a hemisphere
a. I & II b. I & IV c. II & III d. I, II & III e. I, II, & IV
For a curved mirror, the law of reflection holds for
A) the mirror as with a plane mirror. B) tiny segments that act as plane surfaces. C) both convex and concave mirrors. D) only convex mirrors.
Car B is traveling twice as fast as car A, but car A has twice the mass of car B. Which car has the greater kinetic energy and by what factor is it greater?
A 2.0-m rope is lying on a table. You pick up one end and start raising it vertically. How high above the table is the center of mass (or center of gravity) of the rope when half of the rope has lifted off the table?
A) 0.25 m B) 0.50 m C) 0.75 m D) 1.0 m E) 1.5 m