A blacksmith is flattening a steel plate, 10 cm × 15 cm × 1 mm. He has heated the plate to 900 K. If the emissivity of the plate is 0.75, what is the total rate of radiation of energy?
The Stefan-Boltzmann constant is 5.67 × 10-8 W/(m2?K4). Ignore heat exchange with the surroundings.
A)
360 W
B)
760 W
C)
790 W
D)
850 W
E)
880 W
D
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A. 199 N B. 91 N C. 145 N D. 279 N
If the work done to stretch a spring by 4.0 cm is 6.0 J, what is the spring constant?
A) 300 N/m B) 3000 N/m C) 3500 N/m D) 7500 N/m E) 6000 N/m
Two ceramic cylinders have the following properties. Cylinder A has radius R and height 2H, while Cylinder B has radius 3R and height H/4. Their resistances are measured, and it is found that 
What is the ratio of the resistivities 
of the ceramics from which they are made?
A. 1/36 B. 9/8 C. 16/9 D. 1/18 E. 36 F. 9/4
Atomic Nucleus: The atomic number and mass number for calcium-39 are 20 and 39, respectively. How many neutrons are in one atom?
A. 1 B. 19 C. 20 D. 39 E. 59