What is the common trait of all main-sequence stars?
A) They are all spectral type G.
B) They generate energy through hydrogen fusion in their core.
C) They all have approximately the same mass.
D) They are in the final stage of their lives.
B
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The diagram shows three isotherms for an ideal gas, with T3 ? T2 the same as T2 ? T1. It also shows five thermodynamic processes carried out on the gas. Rank the processes in order of the change in the internal energy of th gas, least to greatest.
A. I, II, III, IV, V B. V, then I, III, and IV tied, then II C. V, I, then III and IV tied, then II D. IV, V, III, I, II E. II, I, then III, IV, and V tied
A weight of 200 N is hung from a spring with a spring constant of 2500 N/m and lowered slowly. How much will the spring stretch?
A) 4.00 cm B) 6.00 cm C) 8.00 cm D) 10.0 cm E) 12.0 cm
Galaxies with disks but no evident spiral arms are called
A) irregular galaxies B) lenticular galaxies C) barred spiral galaxies D) elliptical galaxies
Which of the following statements about scientific theories is not true?
A) A theory can never be proved beyond all doubt; we can only hope to collect more and more evidence that might support it. B) A theory cannot be taken seriously by scientists if it contradicts other theories developed by scientists over the past several hundred years. C) A theory is a model designed to explain a number of observed facts. D) A theory must make predictions that can be checked by observation or experiment. E) If even a single new fact is discovered that contradicts what we expect according to a particular theory, then the theory must be revised or discarded.