Which of the five major divisions of chemistry deals exclusively with carbon compounds?
a. Physical chemistry
b. Inorganic chemistry
c. Analytical chemistry
d. Organic chemistry
e. Biochemistry
d
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If you drop a stone into a hole drilled all the way to the other side of Earth (neglect the molten core), the stone will
A) come to an abrupt stop at Earth's center. B) speed up until it gets to Earth's center. C) speed up until it reaches Earth's other side. D) slow down until it reaches Earth's center.
Lifting a 100-N load with 50 N of force lifts it
A) half as high. B) as high. C) twice as high.
The figure shows two point sources of light, A and B, that emit light waves in phase with each other. A is a distance of 3? from point P. B is distant 5? from P. (? is the wavelength.) The phase difference between the waves arriving at P from A and B is
?
?
a.
0 rad.
b.
? rad.
c.
2? rad.
d.
3? rad.
e.
4? rad.
Suppose an engineer suggests that air instead of water could flow through the tube and the velocity of the air could be increased until the heat transfer coefficient with the air equals that obtained with water at 1.5 m/s. Determine the velocity required and comment on the feasibility of the engineer’s suggestion. Note that the speed of sound in air at 100°C is 387 m/s.
GIVEN
• Air flow through a tube
• Bulk inlet air temperature (Tb,in) = 93°C
• Tube diameter (D) = 0.015 m
• Tube length (L) = 0.3 m
• Tube surface temperature (Ts) = 204°C
• From Problem 7.32: h ,c L = 13,037 W/(m2 K)
FIND
• The velocity (V) required to obtain h ,c L = 13,037 W/(m2 K)
ASSUMPTIONS
• Steady state
• Constant and uniform tube temperature
SKETCH
PROPERTIES AND CONSTANTS
for dry air at the inlet bulk temperature of 93°C
Thermal conductivity (k) = 0.0302 W/(m K)
Kinematic viscosity (?) = 22.9 × 10–6 m2/s
Prandtl number (Pr) = 0.71