It takes no work to hold a cheerleader in the air, as shown here. If no work is done by the cheerleaders, why do they eventually tire?
a. Because maintaining the same position for a long time is boring.
b. Their bodies expend chemical energy as their muscles function; this is "hard work," but not the same kind of work that moves a mass over a distance.
c. The concept of work, as it apples in physics, does not apply to any process that involves people.
d. The arrangement is unstable and they can easily fall over.
e. The cheerleaders at the greater height have more potential energy.
b
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The temperature is such that the rms speed of nitrogen molecules is 900. m/s at 750. mm Hg pressure
If the pressure increases to 780. mm Hg while the temperature remains constant, what is the rms speed now? [Molecular weight of nitrogen molecule is 28.]
Springs: An ideal spring stretches by 21.0 cm when a 135-N object is hung from it. If instead you hang a fish from this spring, what is the weight of a fish that would stretch the spring by 31.0 cm?
A. 199 N B. 91 N C. 145 N D. 279 N
If we know the size of an asteroid, how can we determine its density?
A) comparing its reflectivity to the amount of light it reflects B) looking for brightness variations as it rotates C) determining its mass from its gravitational pull on a spacecraft, satellite, or planet D) radar mapping E) spectroscopic imaging
Because HF, hydrogen fluoride, is a covalent gaseous molecule at room temperature, we might reasonably expect that at room temperature HCl, hydrogen chloride, is
a. a covalent gaseous molecule. b. a covalent solid. c. a metallic gas. d. a metallic solid. e. an ionic solid.