How many focal points does a lens have?
a. None.
b. One.
c. Two.
d. Three.
e. An infinite number of possible locations.
c
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Hot water is used to heat air in a double pipe heat exchanger as shown in the following sketch. If the heat transfer coefficients on the water side and on the air side are 550 W/(m2K) and 55 W/(m2 K), respectively, calculate the overall heat transfer coefficient based on the outer diameter. The heat exchanger pipe is 5 cm, schedule 40 steel (k = 54 W/m K), with water inside.
GIVEN
• A double pipe heat exchanger with water in inner tube and air in the annulus
• Heat transfer coefficients
? Water side ih = 550 W/(m2 K)
? Air side oh = 55 W/(m2 K)
• Inner pipe: 5 cm, schedule 40 steel
• Pipe thermal conductivity (k) = 54 W/(m K)
FIND
• The overall heat transfer coefficient based on the outer diameter (Uo). ASSUMPTIONS
• Uniform heat transfer coefficients
SKETCH
PROPERTIES AND CONSTANTS
for 5 cm, schedule 40 pipe
? Outside diameter (Do) = 2.375 in = 6.033 cm=0.0603 m
? Wall thickness (t) = 0.154 in=0.39 cm=0.0039 m
Applications to Astronomy: In terms of the mass M of our sun, what is the Chandrasekhar limit of stellar mass, below which a star will eventually collapse into a white dwarf?
A. 0.8 M B. 1.2 M C. 1.4 M D. 1.9 M
The focal lengths of the objective and the eyepiece in a microscope are 0.29 cm and 2.50 cm, respectively. An object is placed at 0.30 cm from the objective lens and the image of this object is viewed with the eyepiece adjusted for minimum eyestrain
The near-point distance of the person using the microscope is 25.0 cm. What is the final magnification of the microscope? A) -190 B) -240 C) -300 D) -310 E) -470
Dark matter in galaxies and clusters of galaxies is purely hypothetical because we have no way of detecting its presence
Indicate whether the statement is true or false