Uranium is found on the Earth, even though it is radioactive. That's because
A. it is constantly made by cosmic rays
B. it has a very long half-life
C. it is created in fusion in the sun
D. it is created by fusion in the Earth
Answer: B. it has a very long half-life
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Density waves may explain
A) the lack of blue stars in the halo. B) the random orbits of halo stars. C) the density of red stars in the bulge. D) the spiral arm structure of the Galaxy. E) the large number of open clusters in the halo.
A wheel rotating about a fixed axis with a constant angular acceleration of 2.0 rad/s2 turns through 2.4 revolutions during a 2.0-s time interval. What is the angular velocity at the end of this time interval?
a. 9.5 rad/s b. 9.7 rad/s c. 9.3 rad/s d. 9.1 rad/s e. 8.8 rad/s
A 20.0-L pressure vessel holds 2.00 moles of oxygen at 30°C. What is the pressure inside the vessel?
A) 101 Pa B) 101 kPa C) 1.01 × 106 Pa D) 2.52 × 106 Pa E) 252 kPa
If the growth rate of the number of solar collectors is 7% per year, then 1000 units in use in 2010 will grow to _______ units by the year 2040
a. 1200 b. 2000 c. 4000 d. 8000 e. 20,000