Sonic Booms: A sonic boom occurs only as an airplane just reaches the speed of sound in air, but not after it increases its speed further.
A. True
B. False
Answer: B
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Two parallel disks shown in the figure have emissivity of 0.6. If one of the disks is at 200ºC and the other one is at 30ºC, (a) determine the net heat transfer between the two disks if the surroundings re-radiate heat and (b) determine the net heat transfer between the two disks if the surroundings are a black body at 20ºC.
Our Earth is about four times larger than the Moon in diameter
Indicate whether the statement is true or false
On a calm day with no wind, you can run a 1500-m race at a velocity of 4.0 m/s. If you run the same race on a day when you have a constant headwind that slows your speed by 2.0 m/s, how much time would it take you to finish the race?
A) 250 s B) 750 s C) 1125 s D) 9000 s
If a radioactive element has a half-life of 5760 years, and the amount of parent material remaining is one-fourth of the original amount, the specimen is about
A) 11,520 years old. B) 17,280 years old. C) 23,040 years old. D) 28,800 years old.