The mass of a single galaxy might be found by
a. the double galaxy method.
b. the rotation curve method.
c. the cluster method.
d. any of these methods.
e. none of these methods.
B
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The 500-m-long spaceship Springbrake is at rest on the planet Hitest for refueling. Another spaceship, Summerbrake, passes parallel to Springbrake at 0.600c. The crew on Springbrake measure the length of Summerbrake as it passes and find that the length they measure is exactly the same as the known 500-m rest length of Springbrake. If Summerbrake were at rest next to Springbrake, its length would then be measured to be
A. 180 m. B. 320 m. C. 500 m. D. 625 m. E. 781 m.
The size and sign of the charge on an electron is the same as that for
a. a positron. b. an antiproton. c. an antineutron. d. an antineutrino.
A lens is used as a magnifier. Which of the following statements is incorrect?
a. The lens is convex. b. The dioptric power of the lens is positive. c. The magnification is greatest when the eye focuses at the near point. d. The focal length of the lens must be negative.
A thin infinitely large current sheet lies in the y-z plane. Current of magnitude Js per unit length along the z axis travels in the y-axis direction, which is up out of the page. Which diagram below correctly represents the direction of the magnetic field on either side of the sheet?
a.
b.
c.
