What direct evidence do astronomers have that supports the heavy element formation in stars?
A) The presence of technetium in giant star spectra
B) Observed elemental abundances
C) Gamma-ray emissions from decay of cobalt 56 in supernovae
D) Light curves of type-I supernovae
E) All of the above are evidence of this.
E
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Newton's Second Law in 1 Dimension: A block is on a frictionless table, on earth. The block accelerates at 5.3 m/s2 when a 10 N horizontal force is applied to it. The block and table are set up on the Moon where the acceleration due to gravity is 1.62 m/s2. A horizontal force of 5 N is now applied to the block when it is on the Moon. The acceleration imparted to the block by this force is closest to
A. 2.7 m/s2. B. 2.4 m/s2. C. 2.9 m/s2. D. 3.2 m/s2. E. 3.4 m/s2.
Lens-Maker Formula: A converging lens with the same curvature on both faces and a focal length of 25 cm is to be made from crown glass having a refractive index of 1.52. What radius of curvature is required for each face?
Fill in the blank(s) with the appropriate word(s).
What causes the radio pulses of a pulsar?
A) The star vibrates. B) As the star spins, beams of radio radiation sweep through space. If one of the beams crosses Earth, we observe a pulse. C) The star undergoes periodic explosions of nuclear fusion that generate radio emission. D) The star's orbiting companion periodically eclipses the radio waves emitted by the main pulsar. E) A black hole near the star absorbs energy and re-emits it as radio waves.
About how hot was the Big Bang when matter and energy "decoupled"?
A) 900 million K B) 15 million K C) 3,000 K D) 300 K E) 2.73 K