The primary way that we observe the atomic hydrogen that makes up most of the interstellar gas in the Milky Way is with
A) radio telescopes observing at a wavelength of 21 centimeters.
B) ground-based visible-light telescopes.
C) space-based ultraviolet telescopes.
D) x-ray telescopes.
A) radio telescopes observing at a wavelength of 21 centimeters.
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Text boxes, check boxes, and option buttons are all elements of what type of web tool?
A. forms B. comments fields C. databases D. login pages
A solid disk and a hoop have different diameters but identical masses. Which one has a larger rotational inertia?
A. The hoop B. The solid disk C. It is impossible to know without knowing the diameters D. It is impossible to know without knowing the torques acting on the two objects
Jerome pitches a baseball of mass 0.300 kg. The ball arrives at home plate with a speed of 40.0 m/s and is batted straight back to Jerome with a return speed of 52.0 m/s. What is the magnitude of change in the ball's momentum?
a. 3.60 kg/m/s b. 12.0 kg/m/s c. 15.6 kg/m/s d. 27.6 kg/m/s e. 12.0 kg/m/s
One of the "nails in the coffin" for Earth-centered universe was
A) the retrograde motion of the planets. B) the phases of the Moon. C) eclipses of the Sun. D) Galileo's observation of stars in the Milky Way. E) Galileo's observations of the moons of Jupiter.