Study this H-R diagram. Which of the following stars has (or had) the longest hydrogen fusing lifetime? (The red arrows help you locate these stars on the diagram.)
A) Barnard's star
B) Alpha Centauri B
C) Betelgeuse
D) the Sun
A) Barnard's star
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At which of these Kelvin temperatures would a blackbody radiate mostly at visible wavelengths?
A) 6 K B) 60 K C) 600 K D) 6000 K E) None of these; a blackbody doesn't radiate visible light.
A railroad freight car, mass 15,000 kg, is allowed to coast along a level track at a speed of 2.0 m/s. It collides and couples with a 60,000-kg loaded second car, initially at rest and with brakes released. What percentage of the initial kinetic energy of the 15,000-kg car is preserved in the two-coupled cars after collision?
a. 20% c. 86% b. 23% d. 100%
A superconducting wire's chief characteristic is which of the following?
a. no resistance c. an extremely great length b. a large cross sectional area d. an extremely high temperature
How far away is a lightning strike if you hear the thunderclap 2.00 s after you see the lightning bolt strike? (vsound = 340 m/s, vlight = 3 × 10^8 m/s)
a. 113 m c. 680 m b. 340 m d. 1020 m