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

Physics & Space Science

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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%

Physics & Space Science

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

Physics & Space Science

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

Physics & Space Science

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.

Physics & Space Science