Bats can detect small objects such as insects that are of a size on the order of a wavelength. If bats emit a chirp at a frequency of 60 kHz and the speed of soundwaves in air is 330 m/s, what is the smallest size insect they can detect?
a. 1.5 mm
b. 3.5 mm
c. 5.5 mm
d. 7.5 mm
e. 9.8 mm
C
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Suppose we increase the absolute temperature of a semiconductor from 200 K to 300 K. By roughly what factor does this make the semiconductor more conductive? (Hint: How much more likely is it for a conduction band energy level to be occupied by an electron?)
A. 1.5 times B. 3 times C. 4.5 times D. 20 times E. One cannot tell with the information given.
The brightness of a lamp is directly related to its
A) brand. B) place of manufacture. C) power rating. D) all of the above E) none of the above
Which of the following best describes the current scientific view of possibilities of travel to distant parts of our galaxy (or universe) with such things as hyperspace, wormholes, or warp drive?
A) We do not know if travel in any of these ways is really possible, but they do not contradict any known laws of physics. B) There is no doubt that such travel is possible, though it remains well beyond our current technology. C) They sound like fun, but they are not possible because they allow faster-than-light travel. D) They seemed to be allowed by special relativity, but general relativity does not allow for them.
In the figure below, a hoop (radius R = 1.0 m, mass = 2.0 kg) having four spokes of negligible mass is suspended from a pivot a distance d = .25 m above its center of mass. The angular frequency (in rad/s) for small oscillations is approximately
?
?
A. 4.0. B. 2.5. C. 1.5. D. 1.0. E. 0.5.