A comet entering the inner solar system from afar will
a. form a tail and some time later form a coma.
b. form a coma and some time later form a tail
c. always form a tail, but only sometimes form a coma
Ans: b. form a coma and some time later form a tail
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What will be an ideal response?
Induction: 
X and Y are two initially uncharged metal spheres on insulating stands, and they are in contact with each other. A positively charged rod R is brought close to X as shown in part (a) of the figure. Sphere Y is now moved away from X, as shown in part (b). What are the final charge states of X and Y?
A. Both X and Y are neutral. B. X is positive and Y is neutral. C. X is neutral and Y is positive. D. X is negative and Y is positive. E. Both X and Y are negative.
The temperature at the bottom of Lake Tahoe, high in the Sierra Nevada Mountains in California, at this moment is
A) below 4°C. B) 4°C. C) above 4°C. D) uncertain.
Which of the following statements about electrons is not true?
A) Electrons orbit the nucleus rather like planets orbiting the Sun. B) Within an atom, an electron can have only particular energies. C) Electrons can jump between energy levels in an atom only if they receive or give up an amount of energy equal to the difference in energy between the energy levels. D) An electron has a negative electrical charge. E) Electrons have very little mass compared to protons or neutrons.