A sound with a frequency of 11 Hz is in the ______________ region of the sound spectrum
a. infrasonic
b. ultrasonic
c. audible
d. visible
a
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Reconsider the problem of cooling of a rotating rod (shaft) by natural convection described in Example 8.6. Determine the shaft rotation at which the heat transfer contribution due to the rotation convection is about the same as that due to natural convection, and calculate the total heat transfer rate at this condition. Also, graph the variation of q, as well as its two components (qr and qnc) with shaft rpm ranging from 3 rpm to 15 rpm, and comment upon the results.
GIVEN
? Cooling of rotational shaft by natural convection
? Rod diameter (D) = 20 cm = 0.2 m
? Air temperature (T?) = 20°C
? Temperature of rotating rod (Tb) = 1000°C
FIND
? Shaft rotation at which heat transfer contribution due to rotational convection is same as that due
to natural convection.
? Total heat transfer rate at this condition.
? Graph of variation of q and qr and qnc with shaft rpm.
ASSUMPTIONS
? Radiation is negligible
? The shaft is horizontal
PROPERTIES AND CONSTANTS
Which is a consequence of the synchronous orbit of the Earth's Moon (equal period ofrotation and revolution) ?
a) lunar eclipses b) phases of the Moon c) same side of the Moon always faces the Earth d) solar eclipses e) craters on the Moon
Which of the following best describes the lunar maria?
A) densely cratered regions on the Moon B) mountainous regions on the Moon C) frozen oceans of liquid water on the Moon D) relatively smooth, flat plains on the Moon
A current carrying wire placed in a magnetic field perpendicular to the wire experiences a maximum force
Indicate whether the statement is true or false