The mass of a hot-air balloon and its cargo (not including the air inside) is 250 kg. The air outside is at a temperature of 10°C and a pressure of 1 atm = 105 N/m2 . The volume of the balloon is 400 m3 . Which temperature below of the air in the balloon will allow the balloon to just lift off? (Air density at 10°C is 1.25 kg/m3.)
a. 37°C
c. 99°C
b. 293°C
d. 200°C
B
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Two point charges, separated by 1.5 cm, have charge values of +2.0 and -4.0 µC, respectively. Suppose we determine that 10 field lines radiate out from the +2.0-µC charge. If so, what might be inferred about the -4.0 mC charge with respect to field lines?
a. 40 radiate in c. 5 radiate out b. 20 radiate out d. 20 radiate in
Which of the following stars is an example of a spectroscopic binary system?
A) Mizar B) Triton C) Europa D) Ceres
The half-life of carbon 14 is 5730 years. If a 1-gram sample of old carbon is 1/8 as radioactive as 1-gram of a current sample, then the age of the old sample is about
A) 716 years. B) 11,500 years. C) 17,200 years. D) 22,900 years. E) 46,000 years.
We can describe a location on Earth's surface by stating its
A) altitude and direction (or azimuth). B) meridian and longitude. C) latitude and direction. D) latitude and longitude.