The Physical Activity Guidelines for Americans specify that people need to spend at least _____ minutes performing moderate-intensity aerobic activity on five to seven days per week.
a. ?60
b. ?20?
c. 30
d. 45?
e. ?75
Answer: c. 30
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What technology do astronomers use to search for extraterrestrial life??
a. space observatories
b. radio telescopes
c. refracting telescopes
d. reflecting telescopes
e. FM radio and televisions
The SI unit of length, the meter, is currently defined
A) as 10-7 of the distance from the North Pole to the equator along a meridian running through Paris. B) as the length of the path traveled by light in a vacuum during 1/299792485 s. C) by the President's foot. D) as the distance between two marks on a metal bar make of a platinum-iridium alloy kept at the National Bureau of Standards. E) 1,553,164.1 wavelengths of red cadmium light in dry air at 25°C.
A certain thermodynamic engine extracts 1.30 kJ of thermal energy from a hot temperature reservoir and discharges 0.70 kJ of energy to a cold temperature reservoir. What is the efficiency of this engine?
A) 46% B) 54% C) 86% D) 27% E) 13%
A 40.0-g block of ice at -15.00°C is dropped into a calorimeter (of negligible heat capacity) containing water at 15.00°C. When equilibrium is reached, the final temperature is 8.00°C
How much water did the calorimeter contain initially? The specific heat of ice is 2090 J/kg ? K, that of water is 4186 J/kg ? K, and the latent heat of fusion of water is 33.5 × 104 J/kg. A) 302 g B) 345 g C) 405 g D) 546 g E) 634 g