Which of the following increases the internal energy of a solid metal rod?
a. raising it to a greater height
b. throwing it through the air
c. having the rod conduct heat
d. having the rod absorb heat
d
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A long wooden rod at 38°C with a 2.5 cm OD is placed into an airstream at 600°C. The heat transfer coefficient between the rod and air is 28.4 W/(m2 K). If the ignition temperature of the wood is 427°C, ? = 800 kg/m3, k = 0.173 W/(m K), and c = 2500 J/(kg K), determine the time between initial exposure and ignition of the wood.
GIVEN
• A long wooden rod is placed into an airstream
• Rod outside diameter (D) = 2.5 cm = 0.025 m
• Initial temperature of the rod (To) = 38°C
• Temperature of the airstream (T?) = 816°C
• The heat transfer coefficient (hc) = 28.4 W/(m2 K)
• The ignition temperature of the wood (TI) = 427°C
• Density of the rod (?) = 800 kg/m3
• Thermal conductivity (k) = 0.173 W/(m K)
• Specific heat (c) = 2500 J/(kg K)
FIND
• The time between initial exposure and ignition of the wood
SKETCH
Which of the following best describes the axes of a Hertzsprung-Russell (H-R) diagram?
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A. 0.40 A B. 0.50 A C. 0.60 A D. 0.70 A E. 0.80 A
If we wished to construct a "tank circuit" where electric charge originally stored on a capacitor flows through an inductor, then back again, what value of inductance should we place in series with a fully-charged 100 ?F capacitor to get the circuit to resonate at 60.0 Hz?