A homeowner has a new oil furnace which has an efficiency of 60%. For every 100 barrels of oil needed to heat his house, how much (in barrels of oil) goes up the chimney as waste heat?
a. 20
b. 60
c. 40
d. 80
e. 10
C
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A machine gun, of mass 35. kg, fires 50. gram bullets, with a muzzle velocity of 750. m/s, at the rate of 300. rounds per minute. What is the average force exerted on the machine gun mount?
What will be an ideal response?
Based on the definition of apparent brightness, which units are appropriate for its measurement?
A) watts B) joules C) watts per square meter D) Newtons
An enclosed chamber with sound absorbing walls has a 2.0 m × 1.0 m opening for an outside window. A loudspeaker is located outdoors, 78 m away and facing the window
The intensity level of the sound entering the window space from the loudspeaker is 79 dB. Assume the acoustic output of the loudspeaker is uniform in all directions and that the acoustic energy incident upon the ground is completely absorbed and therefore is not reflected into the window. The threshold of hearing is 1.0 × 10-12 W/m2. The acoustic power entering through the window space is closest to A) 160 µW. B) 79 µW. C) 320 µW. D) 790 µW. E) 1600 µW.
A person carries a mass of 10 kg and walks along the +x-axis for a distance of 100m with a constant velocity of 2 m/s. What is the work done by this person?
A) 0 J B) 20 J C) 200 J D) 1000 J E) None of the other choices is correct.