Pulsating variable stars are useful in determining
a. the mass of a star for which the distance is known.
b. the temperature of a star for which we know the luminosity.
c. the radius of the bulge of our galaxy.
d. the distance to globular clusters.
e. the mass of the Milky Way galaxy.
d
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As shown in the diagram, you've just thrown a baseball toward Al at 100 km/hr, while he is moving away from you to the right at 90 km/hr. According to Al, what is the baseball doing?
A) traveling to the right at 10 km/hr B) traveling to the right at 100 km/hr C) staying stationary D) traveling to the right at 190 km/hr
An electric heater is rated 300W 110V. The safety fuse in the circuit can withstand 15 A of current. How many heaters can be safely operated in the circuit?
A) 2 B) 3 C) 4 D) 5 E) more than 5
Three identical 50-kg balls are held at the corners of an equilateral triangle, 30 cm on each side
If one of the balls is released, what is the magnitude of its initial acceleration if the only forces acting on it are the gravitational forces due to the other two masses? (G = 6.67 × 10-11 N ? m2/kg2 ) A) 4.2 × 10-8 m/s2 B) 3.7 × 10-8 m/s2 C) 1.9 × 10-8 m/s2 D) 6.4 × 10-8 m/s2 E) 2.5 × 10-8 m/s2
The remaining core of a planetary nebula is called a _______________
a. white dwarf b. neutron star c. black hole d. red giant