Why did fusion cease only about 5 minutes after the Big Bang (at the end of the era of nucleosynthesis)?
A) The density of the universe became too low.
B) There was no long any more hydrogen available for fusion reactions.
C) Too many heavy elements were produced.
D) Neutrinos carried off too much energy.
A) The density of the universe became too low.
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If the earth's electric field is 100 N/C downward, what must be the charge on a 1-kg object so that it would be "weightless"?
A) 9.8 C B) 0.22 C C) 1.0 C D) -9.8 × 10-2 C E) 9.8 × 10-2 C
Approximately how many times does an average human heart beat in a lifetime?
A) 3 × 1011 B) 3 × 1010 C) 3 × 109 D) 3 × 108 E) 4 × 107
Why aren't optical or radio telescopes used in particle astronomy, which studies cosmic waves and gravity waves? a. Cosmic and gravity waves are too dangerous to detect
b. Particle astronomy can only be studied in deep space. c. Cosmic and gravity waves are too large of particles for ground-based telescopes. d. Optical and radio telescopes can only detect electromagnetic radiation. e. Optical and radio telescopes are not technologically advanced enough to capture these particles.
Waves on a String: The speed of sound in steel is 5000 m/s. What is the wavelength of a sound wave of frequency 660 Hz in steel?
A. 7.58 m B. 2.41 m C. 1.21 m D. 0.829 m E. 0.132 m