What is the net power that a dog with surface area of 0.075 m2 radiates if his emissivity is 0.75, his skin temperature is 315 K, and he is in a room with a temperature of 290 K? The Stefan-Boltzmann constant is 5.67 × 10-8 W/(m2?K4)
A)
8.8 W
B)
6.0 W
C)
8.0 W
D)
15 W
E)
18 W
A
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Air at 16°C and atmospheric pressure enters a 1.25-cm-ID tube at 30 m/s. For an average wall temperature of 100°C, determine the discharge temperature of the air and the pressure drop if the pipe is (a) 10-cm-long and (b) 102-cm-long.
GIVEN
• Atmospheric air flowing through a tube
• Entering air temperature (Tb,in) = 16°C
• Tube inside diameter (D) = 1.25 cm = 0.0125 m
• Air velocity (V) = 30 m/s
• Average wall surface temperature (Ts) = 100°C
FIND
The discharge temperature (Tb,out) and the pressure drop (?p) if the pipe length (L) is
(a) 10 cm (0.1 m) (b) 102 cm (1.02 m)
ASSUMPTIONS
• Steady state
• The tube is smooth
SKETCH
for dry air at the entering bulk temperature of 16°C
Density (?) = 1.182 kg/m3
Thermal conductivity (k) = 0.0248 W/(m K)
Kinematic viscosity (?) = 15.3 × 10–6 m2/s
Prandtl number (Pr) = 0.71
Specific heat (c) = 1012 J/(kg K)
If a person weighs 150 lb on Earth, what will the person weigh on the Moon?
a. 25 lb b. 900 lb c. 150 lb d. 75 lb e. 300 lb
In the reaction 
how much energy is released or absorbed? The mass of 4He is 4.0026032 u, the mass of 9Be is 9.0121821 u, the mass of n is 1.0086649 u, and the mass of 12C is 12.0000000 u.
A. 4.21 MeV absorbed B. 4.21 MeV released C. 5.70 MeV absorbed D. 5.70 MeV released E. 6.34 MeV released
All electromagnetic waves have the same physical characteristics. They differ only in frequency and wavelength. How are they classified into different types?