What is the shortest wavelength of a photon that can be emitted by a hydrogen atom, for which the initial state is n = 3? (c = 3.00 × 108 m/s, h = 6.626 × 10-34 J ? s, 1 eV = 1.60 × 10-19 J)
A) 822 nm B) 850 nm C) 950 nm D) 91.4 nm E) 103 nm
E
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A coin and a ring roll down an incline at the same time. The one to first reach the bottom is the
A) ring. B) coin. C) both reach the bottom at the same time
How many calories of heat are required to raise the temperature of 4 kg of water from 50°F to the boiling point?
a. 6.5 × 10^5 b. 3.6 × 10^5 c. 15 × 10^5 d. 360 e. 4 × 10^4
including a contact resistance of 0.1 K/W at each of the interfaces. but assume that instead of surface temperatures, the given temperatures are those of air on the left and right sides of the wall and that the convective heat transfer coefficients on the left and right surfaces are 6 and 10 W/(m2K), respectively.
GIVEN
• Composite wall
• Thermal conductivities
? kA = 70 W/(m K)
? kB = 60 W/(m K)
? kC = 40 W/(m K)
? kD = 20 W/(m K)
• Air temperatures
? Left side (TA?) = 200°C
? Right side (TD?) = 50°C
• Contact resistance at each interface (Ri) = 0.1 K/W
• Convective heat transfer coefficients
? Left side ( cA h ) = 6 W/(m2 K)
? Right side ( cD h ) = 10 W/(m2 K)
FIND
(a) Rate of heat transfer through the wall (q) (b) Temperatures at the interfaces
ASSUMPTIONS
• One dimensional, steady state conduction
SKETCH
When one kilogram of uranium undergoes nuclear fission,
A) the total amount of rest-mass is conserved. B) the total amount of energy is conserved. C) Both of the above. D) Neither of the above.