The Palomar reflecting telescope has a parabolic mirror with an 80-m focal length. What is the magnification achieved when an eyepiece of focal length 2.5 cm is used?
a. 800
b. 1,100
c. 1,600
d. 3,200
e. 2,000
d
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The test data tabulated on the next page were reduced from measurements made to determine the heat-transfer coefficient inside tubes at Reynolds numbers only slightly above transition and at relatively high Prandtl numbers (as associated with oils). Tests were made in a double-tube exchanger with a counterflow of water to provide the cooling. The pipe used to carry the oils was 1.5 cm-OD, 18 BWG, 3 m-long. Correlate the data in terms of appropriate dimensionless parameters.
Hint: Start by correlating Nu and ReD irrespective of the Prandtl numbers, since the influence of
the Prandtl number on the Nusselt number is expected to be relatively small. By plotting Nu vs.
Re on log-log paper, one can guess the nature of the correlation equation, Nu = f1 (Re). A plot of
Nu/f1 (Re) vs. Pr then reveals the dependence upon Pr. For the final equation, the influence of
the viscosity variation also is considered.
GIVEN
Oil in a counterflow heat exchanger
Pipe specifications: 1.5 cm-OD, 18 BWG
Pipe length (L) = 3 m
The experimental data above
FIND
Correlate the data in terms of appropriate dimensionless parameters
ASSUMPTIONS
The data represents the steady state for each case
PROPERTIES AND CONSTANTS
From Appendix 2, Table 42: for 1.5 cm OD, 18 BWG tubing, the inside diameter D = 1.338 cm
Besides Earth, which of the terrestrial planets and/or satellites of terrestrial planets show(s) evidence for the possible existence of liquid water flowing on its surface in the past?
a. Venus b. The Moon c. Phobos d. Mars e. None of the terrestrial planets or satellites show such evidence.
Where did helium come from the early Universe?
A. The early Universe was so hot and dense that fusion of protons (hydrogen) into helium could occur. B. Photons bombarded hydrogen atoms and broke them up into helium atoms. C. Helium was formed in the cores of stars formed in the early Universe. D. Helium was not formed in the early Universe, because only neutrons were present.
Magnifying Glass With the Image at Infinity: A person uses a converging lens of focal length 5.0 cm as a magnifying glass. What is the angular magnification if the person's eye is relaxed and has a near point of 25 cm?
A. 4.0 B. 5.0 C. 6.0 D. 7.0