Calorimetry: An 920-g piece of iron at 100°C is dropped into a calorimeter of negligible heat capacity containing 50 g of ice at 0°C and 92 g of water, also at 0°C. What is the final temperature of the system? The specific heat of iron is 448 J/kg ? K, that of water is 4186 J/kg ? K, and the latent heat of fusion of water is 33.5 × 104 J/kg.
A. 0°C
B. 11°C
C. 14°C
D. 24°C
E. 32°C
Answer: D
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A long steel rod (2 cm in diameter, 2-m-long) has been heat-treated and quenched to a temperature of 100°C in an oil bath. To cool the rod further, it is necessary to remove it from the bath and expose it to room air. Will the faster cool-down result from cooling the cylinder in the vertical or horizontal position? How long will the two methods require to allow the rod to cool to 40°C in 20°C air?
GIVEN • A long steel rod in air • Diameter (D) = 2 cm = 0.02 m • Length (L) = 2 m • Initial temperature (Ts,i) = 100°C • Air temperature (T?) = 20°C FIND (a) Is it faster to cool the rod vertically or horizontally? (b) Time for rod to cool to 40°C in each position ASSUMPTIONS • Steel is 1% carbon PROPERTIES AND CONSTANTS for 1% carbon steel Thermal conductivity (ks) = 43 W/(m K) Specific heat (c) = 473 J/(kg K) Density (?) = 7801 kg/m3 for dry air at the initial mean temperature of 60°C Thermal expansion coefficient (?) = 0.003 1/K Thermal conductivity (k) = 0.0279 W/(m K) Kinematic viscosity (?) = 19.4 × 10–6 m2/s Prandtl number (Pr) = 0.71
On planet X, the absolute pressure at a depth of 2.00 m below the surface of a liquid nitrogen lake is 5.00 × 105 N/m2. At a depth 5.00 m below the surface, the absolute pressure is 8.00 × 105 N/m2. The density of liquid nitrogen is 808 kg/m3
(a) What is the atmospheric pressure on planet X? (b) What is the acceleration due to gravity on planet X? What will be an ideal response?
A water-filled paper cup held in a flame will not catch fire because
A) the inside of the paper is wet. B) water is an excellent conductor of heat. C) paper is a good conductor of heat. D) the paper cup cannot become appreciably hotter than the water it contains.
The different colors of the spectrum
A) are sharply divided. B) blend from one to another. C) differ from the colors of a rainbow.