Briefly describe the order of creation of normal matter in the Big Bang
What will be an ideal response?
Radiation originally filled the entire universe. There was sufficient energy for photons to transform into stable protons and neutrons. As temperatures dropped, electrons and positrons were formed next. Meanwhile, the protons and neutrons fused to make deuterium, and deuterium fusion led to helium production in the first few minutes. As the temperature fell still more, this production ceased, and finally at decoupling, electrons began to orbit the protons to form neutral hydrogen atoms.
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A piece of wood 350 mm × 350 mm and 15 mm thick conducts heat through its thickness under steady state conditions. The rate of heat flow is measured to be 14.0 watts when the temperature difference is 28 C°
Determine the coefficient of thermal conductivity for this wood A) 9.2 × 10-4 J/(m?s?C°) B) 270 J/(m?s?C°) C) 16 J/(m?s?C°) D) 0.061 J/(m?s?C°) E) 33 J/(m?s?C°)
If you do work on a skateboard loaded with friends in one-third the usual time, you expend
A) one third as much power. B) the usual power. C) three times the usual power. D) need more information.
A Young's double-slit apparatus is set up where a screen is positioned 1.2 m from the double slits. If the distance between alternating bright fringes is 0.83 cm, and the light source has a wavelength of 579 nm, what is the separation of the double slits? (1 nm = 10?9 m)
a. 1.2E–2 m b. 8.4E–5 m c. 7.0E–6 m d. 9.0E–5 m e. 4.0E–9 m
If a magnet produces a force on a current-carrying wire, the wire
A) produces a force on the magnet. B) may or may not produce a force on the magnet. C) none of these