A blacksmith is flattening a steel plate having dimensions 10 cm × 15 cm × 1 mm. He has heated the plate to 900 K
If the emissivity of the plate is 0.75, at what rate does it lose energy by radiation? Ignore any heat exchange with the surroundings. (? = 5.67 × 10-8 W/m2 ? K4 )
A) 850 W B) 790 W C) 760 W D) 880 W E) 360 W
A
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Suppose you have a spool of thread that can rotate around a fixed axis as you pull thread off it. If you pull the thread with your hand so that the thread always lies along a certain fixed line, how will your hand’s speed as it moves compare to 
, where R is the spool’s radius and 
is angular speed?
A. The hand’s speed will be greater than 
.
B. The hand’s speed will be less than .
C. The hand’s speed will be equal to .
D. The hand’s speed has nothing to do with .
When a beam of light, originally traveling in air, enters a piece of glass having an index of refraction of 3/2, its frequency
A) is unaffected. B) is reduced to 2/3 its original value. C) increases by a factor of 3/2.
The energy of an electron in the p-level of an atom is changed in the presence of a magnetic field of magnitude 4.6 T
What is the difference between the largest and smallest possible energies? (Bohr magneton = ?B = 9.27 × 10-24 J/T)
Which relative dating principle states that in an undeformed sequence of sedimentary rocks, each layer is older than the one above and younger than the one below?
A) original horizontality B) superposition C) cross-cutting D) inclusion