The choices below each describe the appearance of an H-R diagram for a different star cluster. Which cluster is the youngest?
A) The diagram shows main-sequence stars of every spectral type except O, along with a few giants and supergiants.
B) The diagram shows main-sequence stars of spectral types G, K, and M, along with numerous giants and white dwarfs.
C) The diagram shows main-sequence stars of all the spectral types except O and B, along with a few giants and supergiants.
D) The diagram shows no main-sequence stars at all, but it has numerous supergiants and white dwarfs.
A) The diagram shows main-sequence stars of every spectral type except O, along with a few giants and supergiants.
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Which one of the hydrogen atoms below is EMITTING light at a wavelength in the Balmer series?
a. second energy level to first (most bound) b. third energy level to second c. fourth energy level to third d. second energy level to third e. first energy level to second
A 6.1-kg solid sphere, made of metal whose density is 2600 kg/m3, is suspended by a cord. When the sphere is immersed in a liquid of unknown density, the tension in the cord is 26 N. Find the density of the liquid
A) 1500 kg/m3 B) 1400 kg/m3 C) 1300 kg/m3 D) 1200 kg/m3 E) 1100 kg/m3
Glass is transparent to light of frequencies that
A) match its natural frequencies. B) are below its natural frequencies. C) both of these D) none of the above
A child is trying to throw a ball over a fence. She gives the ball an initial speed of 8.0 m/s at an angle of 40° above the horizontal. The ball leaves her hand 1.0 m above the ground and the fence is 2.0 m high
The ball just clears the fence while still traveling upwards and experiences no significant air resistance. How far is the child from the fence? A) 0.73 m B) 1.6 m C) 2.7 m D) 3.8 m E) 7.5 m