At what rate is the gravitational force on a 2.0-kg projectile doing work at an instant when the velocity of the projectile is 4.0 m/s directed 30° above the horizontal?
a. +39 W
b. ?78 W
c. ?39 W
d. +78 W
e. +25 W
c
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Centaurus A is a radio galaxy that has a visible galaxy at the center. This central elliptical galaxy of Centaurus A is encircled by a ring of gas and dust, different from most elliptical galaxies. The dust ring orbits about an axis that is perpendicular to the axis of rotation of the elliptical galaxy. What does this suggest about this central elliptical galaxy of Centaurus A?
a. The radio jets have caused the dust disk to be driven around the elliptical galaxy. b. There are at least two black holes at the center of the elliptical galaxy. c. Centaurus A is probably the result of a merger of an elliptical galaxy and a spiral galaxy. d. Dust is produced as the jets interact with the intergalactic medium. e. Elliptical galaxies often contain dust that forms a disk along their rotation axis.
Explain an action-reaction force pair in your own words. When I am standing on the ground at rest, the ground pushes up on my feet and gravity pulls down on me. Do these forces have the same magnitude? Is this an action-reaction pair? Why or why not?
Very low-intensity light passing through a double slit produces a pattern that
A) is built up one photon at a time. B) reveals which slit each photon passed through. C) changes only in intensity as time passes, not in detailed structure.
Who won the Nobel Prize for explaining the photoelectric effect?
a. Bohr b. Planck c. de Broglie d. Einstein