In a visual binary system with circular orbits, if in 20 years the two stars' position angles have shifted by 30 degrees, the pair's period must be:
A) 60 years.
B) 90 years.
C) 120 years.
D) 240 years.
E) 360 years.
D
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A standard candle is
A) a 7-cm-long wax candle. B) another name for a main-sequence star. C) another name for a barred-spiral galaxy. D) a light source of known luminosity.
Which statement about planetary rings is not true?
A) Rings are always located closer to a planet's surface than any large moons. B) Individual ring particles orbit their planet in accord with Kepler's laws, so that particles closer in orbit faster than particles farther out. C) Saturn's rings formed along with its moons 4.6 billion years ago. D) All four jovian planets have rings.
A 30.0-kg child sits on one end of a long uniform beam with a mass 20.0 kg and a 40.0-kg child sits on the other end. The beam balances when a fulcrum is placed below the beam a distance 1.10 m from the 30.0-kg child. How long is the beam?
A) 2.12 m B) 1.98 m C) 1.93 m D) 2.07 m E) 2.20 m
A 0.12-kg ball is moving at 6.0 m/s when it is hit by a bat, causing it to reverse direction and have a speed of 8.0 m/s. What is the magnitude of the change in the momentum of the ball?
a. 0.39 kgm/s c. 1.7 kgm/s b. 0.42 kgm/s d. 2.4 kgm/s