Why are shadows generally not totally black?
a. Because our eyes cannot see total blackness, so we reinterpret the shadows.
b. Because of the way the light is focused by the eye.
c. Because of scattered light from the atmosphere and nearby objects.
d. Because of the fuzziness of the penumbra.
e. Because of the fuzziness of the umbra.
c
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Which of the following statements about spectral types of stars is not generally true?
A) The spectral type of a star can be used to determine its distance. B) The spectral type of a star can be used to determine its surface temperature. C) The spectral type of a star can be used to determine its color. D) The spectral type of a star can be determined by identifying lines in the star's spectrum.
A 90-gram wire that is 1.0 m long is under tension. When a transverse wave of frequency 890 Hz travels down the wire, its wavelength is 0.10 m and its amplitude is 6.5 mm. What is the tension in the wire?
A) 710 N B) 820 N C) 930 N D) 1000 N E) 1100 N
Pressure: A 100-kg person sits on a 5-kg bicycle. The total weight is borne equally by the two wheels of the bicycle. The tires are 2.0 cm wide and are inflated to a gauge pressure of 8.0 × 105 Pa. What length of each tire is in contact with the ground?
A. 1.6 cm B. 1.8 cm C. 3.2 cm D. 2.4 cm E. 6.4 cm
A racecar driver steps on the gas, and his racecar travels 20 meters in 2 seconds starting from rest. The acceleration of the racecar is
a. 0 b. 5 m/s2. c. 9.8 m/s2. d. 10 m/s2. e. 20 m/s2.