An enclosed chamber with sound absorbing walls has a 2.0 m × 1.0 m opening for an outside window. A loudspeaker is located outdoors, 78 m away and facing the window
The intensity level of the sound entering the window space from the loudspeaker is 79 dB. Assume the acoustic output of the loudspeaker is uniform in all directions and that the acoustic energy incident upon the ground is completely absorbed and therefore is not reflected into the window. The threshold of hearing is 1.0 × 10-12 W/m2. The acoustic power entering through the window space is closest to A) 160 µW.
B) 79 µW.
C) 320 µW.
D) 790 µW.
E) 1600 µW.
A
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A) the bullet B) the proton C) both the same
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When material expanding away from a star in a binary system leaves a star’s Roche lobe,
a. the material will start to fall back toward the star.
b. all of the material will accrete on to the companion.
c. the material is no longer gravitationally bound to that star.
d. the material will increase in temperature an eventually undergo thermonuclear fusion.
e. c and d.
The energy for plate tectonics comes primarily from radioactive decay in our core
Indicate whether the statement is true or false