Radio maps of the spiral arms of our galaxy
a. reveal that our galaxy is a grand design spiral.
b. map the location of Hot O and B stars by the radio radiation they emit.
c. reveal that the spiral arms are winding up and growing closer together.
d. reveal that the sun is currently located in the center of a spiral arm.
e. map the location of dense neutral hydrogen clouds.
E
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____ are crucial in determining the distance to objects that are far away, but still in the Milky Way galaxy
a. RR Lyrae stars b. Cepheid variable stars c. O and B stars d. Emission nebulae e. Supernovae
According to our present theory of solar system formation, how did Earth end up with enough water to make oceans?
A) The water was mixed in the other materials in the planetesimals that accreted at our distance from the Sun. B) The water was formed by chemical reactions among the minerals in the Earth's core. C) The water was brought to the forming Earth by planetesimals that accreted beyond the orbit of Mars. D) Earth formed in the relatively narrow region of the solar nebular in which liquid water was plentiful.
How might you separate a mixture of sand and salt?
A) with tweezers and a magnifying glass B) just add water C) heat the mixture until one of the components melts D) Two of the above answers are reasonable.
A 3.50 kg block is pulled along a moving conveyor belt at a constant speed of 0.500 m/s relative to a stationary observer while the belt moves at a constant speed of 0.200 m/s in the opposite direction. If the coefficient of kinetic friction is 0.400, the magnitude of the mechanical energy dissipated, in J, caused by the force of friction on the block in 8.00 s is
a. 5.6. b. 22.0. c. 32.9. d. 54.8. e. 76.8.