How long have mammals been present on Earth?
A) about 1 million years
B) about 65 million years
C) about 225 million years
D) about 510 million years
C) about 225 million years
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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.
The object in a ray diagram is perpendicular to the principal axis but does not have one end lying on the principal axis. The minimum number of rays that must be drawn in this ray diagram in order to determine the position of the image is
A. 1. B. 2. C. 3. D. 4. E. 5.
Which of the following properties of a star can be measured directly, during a single night at the telescope?
A) parallax B) distance C) apparent brightness D) luminosity
Even relatively small astronomical telescopes are ordinarily not used for terrestrial observation because
a. their images are too bright. b. their images are too dim. c. their images are inverted. d. their images are not in color.