What are giant molecular clouds?
a. Cocoons of dust around young protostars, containing giant molecules such as C3H8 and C6H12O6
b. Dark interstellar globules of up to about 30 light-years across and containing a few thousand solar masses of material
c. Bright clouds up to about 100 light-years across surrounding hot, young stars, and glowing with reddish H? emission
d. Star-formation regions of up to about 300 light-years across and containing about a million solar masses of material
Answer is d. Star-formation regions of up to about 300 light-years across and containing about a million solar masses of material. (The famous Orion nebula is part of a giant molecular cloud. The visible nebula has been ionized by the hot, young stars inside it, but behind the visible nebula, star formation is continuing in hidden parts of the cloud.)
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A solid sphere is rolling without slipping along a horizontal surface with a speed of 5.50 m/s when it starts up a ramp that makes an angle of 25.0° with the horizontal. What is the speed of the sphere after it has rolled 3.00 m up the ramp?
A) 4.01 m/s B) 8.02 m/s C) 1.91 m/s D) 2.16 m/s E) 3.53 m/s
Polaris is 10 times larger than Capella A and both are the same color. How much brighter or dimmer is Polaris to Capella?
a. 10× brighter
b. 10× dimmer
c. 100× brighter
d. 100× dimmer
A scalar quantity is described by both a magnitude and a direction
Indicate whether the statement is true or false
Why do astronomers often measure the visible-light apparent brightness instead of the total apparent brightness of a star?
A) All stars put out most of their light in the visible range of the spectrum. B) In order to measure the total apparent brightness of a star, you must measure its brightness in all wavelengths, and this is difficult to do. The only wavelengths you can measure from the surface of Earth are visible and radio wavelengths. C) Most stars do not put out light in other ranges of the spectrum. D) They are identical for most stars. E) Astronomers are lazy.