How are rotation curves of spiral galaxies determined for orbital distances beyond where starlight can be detected?
A) by extrapolation of the measured rotation curve
B) by observations of the 21 cm line of atomic hydrogen
C) by observations of spectral lines emitted by dark matter
D) by watching the galaxies rotate over a period of decades
E) by measuring the broadening of the galaxy's absorption lines
A) by extrapolation of the measured rotation curve
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We observe stars orbiting at distances of 25,000 light-years from the centers of Galaxy X and Galaxy Y. For this orbital distance, stars in Galaxy X have higher orbital speeds than stars in Galaxy Y. What can we conclude?
A) Galaxy X contains more total mass within 25,000 light-years of its center than Galaxy Y. B) Galaxy Y contains more total mass within 25,000 light-years of its center than Galaxy X. C) Galaxy X contains more dark matter than Galaxy Y. D) Galaxy Y contains more dark matter than Galaxy X. E) The stars of Galaxy X are more massive than those of Galaxy Y.
Extrasolar planets are placed in groups by their approximate masses. What are four of these classes?
What will be an ideal response?
A uniform meter stick is pivoted to rotate about a horizontal axis through the 25-cm mark on the stick. The stick is released from rest in a horizontal position. The rotational inertia of a uniform rod about an axis perpendicular to the rod and through the center of mass of the rod is given by (1/12)ML2. Determine the magnitude of the initial angular acceleration of the stick.
A. 17 rad/s2 B. 13 rad/s2 C. 15 rad/s2 D. 19 rad/s2 E. 23 rad/s2
After the switch is closed in a series LR circuit, what is the current when a time equal to four time constants has elapsed?
A. (1/5) Imax B. (15/16) Imax C. (1/16) Imax D. 0.018 Imax E. 0.98 Imax