5. Four stars of equal mass m rotate in a circular path of radius r about their center of mass, as shown in Fig. 3. Their connection lines form a square shape. What is the angular frequency of this rotation motion? (G is the gravitational constant.) (A) (B) (C) (D) (E)

8. Which one of the following statements of the second law of thermodynamics is correct? (A) In a reversible process the entropy of an isolated system stays constant; in an irreversible process the entropy decreases. (B) In a reversible process the entropy of an isolated system increases; in an irreversible process the entropy stays constant. (C) It is impossible for a cyclical device to transfer heat continuously from a cold body to a hot body without the input of work or other effect on the environment. (D) It is possible for a heat engine that operates in a cycle to convert its heat input completely into work. (E) Every cyclical heat engine has a greater efficiency than a reversible engine operating between the same two temperatures.

5. Four stars of equal mass m rotate in a circular path of radius r about their center of mass, as shown in Fig. 3. Their connection lines form a square shape. What is the angular frequency of this rotation motion? (G is the gravitational constant.)

(A)
(B)
(C)
(D)
(E)

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