Astronomy 10 Quiz 10, Spring Semester 2008
Cuesta College, San Luis Obispo, CA
Astronomy 10 learning goal Q10.2
[3.0 points.] Which one of the following choices best explains why the Roche lobes of two stars in a close-pair (mass-exchanging) binary system get smaller as they begin to orbit closer to each other?
(A) Gravitational forces get weaker.
(B) Centrifugal forces get stronger.
(C) Degeneracy pressure increases.
(D) Hydrogen is transferred slowly.
(E) Repeated nova explosions disrupts hydrogen transfer.
Correct answer: (B)
Due to conservation of angular momentum, the orbital speeds of the stars will increase as their separation distance decreases (as they would during hydrogen transfer from a more massive star to a less massive star). This will increase the centrifugal forces exerted on them, decreasing the size of their Roche lobes.
Student responses
Section 5166
(A) : 5 students
(B) : 29 students
(C) : 4 students
(D) : 7 students
(E) : 2 students
Related post:
Astronomy in-class activity: mass transfer in close-pair binaries.
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