Astronomy quiz question: heavy nuclei fusion

Astronomy 10 Quiz 9, Spring Semester 2008
Cuesta College, San Luis Obispo, CA

Astronomy 10 learning goal Q9.4

[3.0 points.] Which one of the following choices best explains why nuclei of elements heavier than hydrogen require higher temperatures to undergo fusion?
(A) Stronger repulsive forces between nuclei.
(B) Stronger gravitational forces between nuclei.
(C) Less energy is contained in heavier nuclei.
(D) More energy is contained in heavier nuclei.
(E) Stronger degeneracy pressures between nuclei.

Correct answer: (A)

All atomic nuclei repel each other, due to their positively charged protons. The relative amount of repulsion between two same-element nuclei depends on the square of the protons contained in a nucleus; it is this repulsion that must be overcome in order for fusion to be initiated.

Student responses
Section 4160
(A) : 17 students
(B) : 5 students
(C) : 2 students
(D) : 4 students
(E) : 8 students

Section 5166
(A) : 30 students
(B) : 5 students
(C) : 2 students
(D) : 16 students
(E) : 4 students