Why do we think the first generation of stars would be different from stars born today?
A) Without heavy elements, the clouds could not reach as low a temperature as today and had to be more massive to collapse.
B) Without heavy elements, the nuclear reactions at the center of the stars would be very different.
C) Without heavy elements, there was no dust in the clouds and they collapsed faster.
D) The Universe was much denser when the first stars were born.
E) There were no galaxies when the first stars were born.
A
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A pair of identical balls is connected by a massless rod, and thrown up into the air. The velocity of the center of mass is initially 17.2 m/s upward. 1.0 s later, one of the balls is measured to be at rest. What is the velocity of the other ball at this time? Ignore air resistance.
A. 14.8 m/s up B. 9.8 m/s down C. 7.4 m/s up D. 7.4 m/s down
When a charged cloud passes overhead, the ground below is charged by
a. induction. b. polarization. c. deduction. d. electrification.
When an electron is formed from a gamma ray collision, a positron is also made
Indicate whether the statement is true or false
One phenomenon that demonstrates the particle nature of light is:
a. the photoelectric effect. b. diffraction effects. c. interference effects. d. the prediction by Maxwell's electromagnetic theory.