Applications to Astronomy: It can be shown that the approximate age of the universe is 1/H, where H is the Hubble constant. Taking H = 20 
, estimate the age of the universe, in years. (1 ly = 9.46 × 1015 m)
A. 15 thousand years
B. 15 million years
C. 15 billion years
D. 50 billion years
Answer: C
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The lift experienced by Maglev trains is due to magnetic
A) attraction. B) repulsion. C) dipoles.
A substance has a melting point of 20°C and a heat of fusion of 3.9 x 104 J/kg. The boiling point is 150°C and the heat of vaporization is 7.8 x 104 J/kg at a pressure of 1.0 atm
The specific heats for the solid, liquid, and gaseous phases are 600 J/(kg?K), 1000 J/(kg?K), and 400 J/(kg?K), respectively. The quantity of heat required to raise the temperature of 3.80 kg of the substance from -61°C to 128°C, at a pressure of 1.0 atm, is closest to A) 620 kJ. B) 470 kJ. C) 560 kJ. D) 210 kJ. E) 770 kJ.
A spring (k = 600 N/m) is at the bottom of a frictionless plane that makes an angle of 30° with the horizontal. The upper end of the spring is depressed 0.10 m, and a 2.0-kg block is placed against the depressed spring. The system is then released from rest. What is the kinetic energy of the block at the instant it has traveled 0.10 m and the spring has returned to its uncompressed length?
a. 2.0 J b. 1.8 J c. 2.2 J d. 1.6 J e. 1.0 J
In addition to Mars, which jovian moon shows some promise of life, with a surface not that different from the Arctic Ocean?
A) Titan B) Miranda C) Europa D) Io E) Triton