Why weren't many elements heavier than helium produced during the nucleosynthesis era?
What will be an ideal response?
By the time helium nuclei could exist in large numbers without being destroyed by the intense radiation field, the universe was about a minute old and the temperature and density were rapidly decreasing. Nuclear fusion reactions to produce heavier elements were possible, but the combination of two helium nuclei or a hydrogen nucleus and helium nucleus produces unstable nuclei. The combination of three helium nuclei can produce carbon, but by this time the density of the universe was too low for many such collisions to occur. Thus the production of heavier elements had to wait until stellar nucleosynthesis.
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An FM radio tuning circuit has a coil with an inductance of 0.0036 mH. What is the value of the capacitance if the set is tuned to 91.3 MHz?
a. 3.38E–12 F b. 2.65E–12 F c. 4.84E–13 F d. 8.45E–13 F e. 8.33E–12 F
Which spectrum is shown above?
a. continuous
b. emission
c. absorption
d. blackbody
The deflection of air and ocean currents from their original direction of motion due to the rotation of Earth is called ________.
A. differentiation B. precession C. revolution D. the Coriolis effect E. circulation
A plane truss composed of two steel pipes (E 5 210 GPa, d 5 100 mm, and wall thickness 5 6.5 mm) is subjected to vertical load W at joint B. Joints A and C are L 5 7 m apart. The critical value of load W for buckling in the plane of the truss is nearly:
(A) 138 kN
(B) 146 kN
(C) 153 kN
(D) 164 kN