Why do elements fuse only in a star's core?
A. Only the core spins fast enough.
B. The fuel settles to the core.
C. Only the core is hot enough for fusion.
D. The statement is incorrect. Fusion occurs just below the surface.
E. None of these choices is correct.
Answer: C
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The first modern astronomer to propose a heliocentric model for the solar system was ____________________
Fill in the blank(s) with correct word
A composite beam of aluminum (Ea 5 72 GPa) and steel (Es 5 190 GPa) has a width b 5 25 mm and heights ha 5 42 mm and hs 5 68 mm, respectively. A bending moment is applied about the z axis resulting in a maximum stress in the aluminum of 55 MPa. The maximum stress in the steel is approximately:
(A) 86 MPa
(B) 90 MPa
(C) 94 MPa
(D) 98 MPa
Which answer below is not a statement of the second law of thermodynamics?
a. Real processes proceed in a preferred direction. b. Energy does not flow spontaneously by heat from a cold to a hot reservoir. c. The entropy of the universe increases in all natural processes. d. In theory, heat engines working in a cycle employ reversible processes. e. You cannot construct a heat engine, operating in a cycle that does nothing but take heat from a reservoir and perform an equal amount of work.
A velocity selector uses a fixed electric field of magnitude E and the magnetic field is varied to select particles of various energies. If a magnetic field of magnitude B is used to select a particle of a certain energy and mass, what magnitude of magnetic field is needed to select a particle of equal mass but twice the energy?
a. 0.50 B b. 1.4 B c. 2.0 B d. 0.71 B e. 1.7 B