A projectile is launched vertically upward at 50 m/s. If air resistance does affect motion, then its speed upon returning to its starting point is
A) less than 50 m/s.
B) 50 m/s.
C) more than 50 m/s.
Answer: A
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Which type of star has the strongest stellar winds?
A) giant K- and M-type stars B) white dwarfs C) dwarf K- and M-type stars D) main sequence O- and B-type stars E) T Tauri stars
What makes white-dwarf supernovae very good standard candles for distance measurements?
A) They are very bright, so they can be used to determine the distances to galaxies billions of light-years away. B) They should all have approximately the same luminosity. C) They occur so frequently that we can use them to measure the distances to virtually all galaxies. D) We have had several occur close to us in the Milky Way, so we have been able to determine their luminosities very accurately. E) both A and B
A laser with a power of 1.0 mW has a beam radius of 1.0 mm. What is the peak value of the electric field in that beam? (c = 3.0 × 108 m/s, ?0 = 4? × 10-7 T • m/A, ?0 = 8.85 × 10-12 C2/N • m2)
A) 490 V/m B) 840 V/m C) 65 V/m D) 120 V/m E) 22 V/m
An object is placed at the center of curvature of a concave mirror. The image is
a. inverted, real, and the same size as the object. b. virtual and the same size as the object. c. virtual and smaller than the object. d. virtual and enlarged. e. erect, real, and the same size as the object.