Astronomy quiz question: hydrostatic equilibrium between fusion and gravity

Astronomy 210 Quiz 6, spring semester 2015
Cuesta College, San Luis Obispo, CA

To maintain a stable size, the sun uses hydrogen fusion to counteract:
(A) gravity.
(B) dark matter.
(C) convection currents.
(D) proton-proton repulsion.

Correct answer (highlight to unhide): (A)

Hydrostatic equilibrium demands that pressure and weight must balance in order for the sun to maintain its stable size; this pressure is generated by the energy released from fusion in its core to support the weight of the outer layers of the sun produced by its gravity.

Section 30674
Exam code: quiz06n1iI
(A) : 15 students
(B) : 2 students
(C) : 10 students
(D) : 9 students

Success level: 46% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): 0.47

Section 30676
Exam code: quiz06szLR
(A) : 27 students
(B) : 0 students
(C) : 12 students
(D) : 13 students

Success level: 61% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): 0.69