Which of the following steps is NOT involved in drownproofing?
A. Swim 10 meters closer to the shore and then relax.
B. Straighten the legs, press arms down, and then inhale.
C. Every 5 to 10 seconds, raise arms, separate legs to lift the mouth above the water, and exhale."
D. Relax in the rest position.
Ans: A. Swim 10 meters closer to the shore and then relax.
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Earth's rotation axis traces out a cone shape in the sky, precessing in the ___________________ direction
Fill in the blank(s) with correct word
A car was moving 110. km/hour
(a) How long did it take to go 25.5 miles? (b) If it stopped in 35. s, what was its average acceleration (m/s2 ) as it slowed down?
When viscous dissipation is appreciable, the conservation of energy [Eq. 5.6] must take into account the rate at which mechanical energy is irreversibly converted to thermal energy due to viscous effects in the fluid. This gives rise to an additional term, Ø , on the right-hand side, the viscous dissipation where
Apply the resulting equation to laminar flow between two infinite parallel plates, with
the upper plate moving at a velocity U. Assuming constant physical properties [p, cp, k,
?], obtain expressions for the velocity and temperature distributions. Compare the
solutions with the dissipation term included with the results when dissipation is
neglected. Find the plate velocity required to produce a 1 K temperature rise in
nominally 40°C air relative to the case where dissipation is neglected.
GIVEN
Laminar flow between two infinite parallel plates
Upper plate moves at a velocity U?
The viscous dissipation term given above must be used in the conservation of energy equation
FIND
(a) Expression for velocity and temperature distributions
(b) Compare these to solutions without the dissipation term
(c) Plate velocity that gives a 1 K rise in 40°C air relative to the case without the dissipation term
ASSUMPTIONS
Steady state
Constant physical properties
The plates are at constant temperatures, T1, T2
SKETCH
PROPERTIES AND CONSTANTS
From Appendix 2, Table 28, for dry air at 40°C
Thermal conductivity (k) = 0.0265 W/(m K)
Absolute viscosity (?) = 19.1 x 10–6 N s/m2
In a double-slit experiment, the slit separation is 2.0 mm, and two wavelengths, 750 nm and 900 nm, illuminate the slits simultaneously. A screen is placed 2.0 m from the slits
At what distance from the central maximum on the screen will a bright fringe from one pattern first coincide with a bright fringe from the other? A) 1.5 mm B) 6.0 mm C) 9.0 mm D) 4.5 mm E) 3.0 mm