Some stars vary in brightness. What observing technique is best for observing the details of the changes in brightness?
A) Time-monitoring because we want to track how the brightness changes with time.
B) Imaging because an image will show the star getting brighter and dimmer.
C) Spectroscopy because changing brightness means changing temperature.
D) All of the above are equally useful in detecting variation in brightness.
A) Time-monitoring because we want to track how the brightness changes with time.
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Two stars of the same spectral class must have the same
a. radius. b. temperature. c. mass. d. distance. e. all of the other choices.
When you see the bright flash of a meteor, what are you actually seeing?
A) the glow of heated air surrounding a small particle as it burns up in our atmosphere B) emission of visible light from a particle that has not yet entered Earth's atmosphere C) a star that has suddenly shot across the sky D) the flash that occurs when a speeding rock from space hits the ground
If a child swinging to and fro on a playground swing stands up, her time for a to-and-fro swing is
A) longer. B) shorter. C) unchanged.
One section of a pipe carrying water has a cross-sectional area of 16 cm2; in this section the water has flow velocity of 1.0 m/s. Another section of this pipe has a constricted cross-sectional area of 4 cm2. If the flow is steady, what is the water velocity in the constricted section?
A. 4.0 m/s B. 0.50 m/s C. 1.0 m/s D. 2.0 m/s E. 0.25 m/s