A lawn mower has a 6-horsepower engine (1 HP = 750 W). If the engine has an efficiency of 20%, and the throttle is such that the engine cycles 10 times a second, the heat that is expelled in one cycle is
a. 1 800 J
b. 2 000 J
c. 2 200 J
d. 2 400 J
e. 2 250 J
a
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Two-Source Interference of Sound: Two in-phase loudspeakers are placed along a wall and are separated by a distance of 4.00 m. They emit sound with a frequency of 514 Hz. A person is standing away from the wall, in front of one of the loudspeakers. What is the closest distance from the wall the person can stand and hear destructive interference? The speed of sound in air is 343 m/s.
A. 0.34 m B. 0.37 m C. 0.73 m D. 1.2 m E. 1.6 m
An automobile engine operates with an overall efficiency of 12%. How much energy is delivered as waste heat (in gallons of gasoline) for each 10 gallons of fuel burned?
a. 1.2 b. 8.8 c. 6.5 d. 4.7 e. 7.5
The current through a piece of lab equipment must be limited to 2.75 A when it is run by a 120-V dc power supply. What must be the resistance of this equipment?
What will be an ideal response?
In the context of electron shells, a positive ion is an atom with:
A) fewer electrons than protons. B) a missing nucleus. C) missing orbits. D) fewer protons than electrons.