Light from inside a raindrop that exits into the air
A) slows down.
B) remains at speed c.
C) speeds up.
D) none of the above
Answer: C
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The principal quantum number can have any integer value ranging from
A) -? to +?. B) 0 to ?. C) 1 to ?. D) 1 to n. E) 1 to 100.
How much thermal energy must be removed from 456 g of water at 25.0°C to change it into ice at -10.0°C?
The specific heat of ice is 2090 J/kg ? K, the latent heat of fusion of water is 33.5 × 104 J/kg, and the specific heat of water is 4186 J/kg ? K. A) 105 kJ B) 153 kJ C) 57.3 kJ D) 47.7 kJ E) 210 kJ
A multi-tube heat exchanger is used in a process plant to pre-heat air before it enters a combustion chamber, using low pressure steam that flows inside the tubes and condenses. The tube bundle is configured with 6-cm outer diameter tubes in a staggered arrangement as shown in the accompanying figure. The condensing steam in the tubes maintains their outer surface temperature at 117°C, and air at 60° flows across the tube bank with a free stream velocity of 1.0 m/s. Determine the average heat transfer coefficient for air.
GIVEN
• Air flow through the tube bank shown
• Air temperature (Ta) = 60°C
• Air velocity (Us) = 1 m/s
• Tube outside diameter (D) = 6 cm = 0.06 m
• Tube wall temperature (Tw) = 117°C FIND
• The average heat transfer coefficient ( ch ) ASSUMPTIONS
• Steady state
PROPERTIES AND CONSTANTS
Thermal conductivity (k) = 0.0279 W/(m
K) Kinematic viscosity (?) = 19.4 × 10–6 m2/s
Prandtl number (Pr) = 0.71 At Tw: Prs = 0.71
Two waves are described by ? y1 = 6 cos(180t?) and y2 = 6 cos(186t) (both in meters). ? What effective frequency does the resultant vibration have at a point?
A. 92 Hz B. 183 Hz C. 6 Hz D. 3 Hz E. 366 Hz