A planar cross section through two spherical waves emanating from the sources S1 and S2 in the plane is shown in the figure. The black circles are one and two wavelengths from their respective sources. The lighter circles are one half and one and a half wavelengths distant from their respective sources. If the phase at S1 and S2 is zero at this instant, and the waves shown arriving at P1 both arrive with amplitude A, the magnitude of the phase angle of each wave at point P1 (in radians) is
A. 0.
B. ?.
C. 2?.
D. 3?.
E. ?/2.
Answer: D
You might also like to view...
Two wires, each having a weight per unit length of 1.0 × 10^?4 N/m, are strung parallel, one 0.10 m above the other. If the wires carry the same current, though in opposite directions, how great must the current in each wire be for the magnetic field of the lower conductor to balance the weight of the upper conductor?
A 1000 kg sports car accelerates from zero to 25 m/s in 6.25 s. What is the average power delivered by the automobile engine?
a. 20.8 kW c. 41.7 kW b. 30.3 kW d. 50.0 kW
A stainless steel pin fin 5-cm-long, 6-mm-OD, extends from a flat plate into a 175 m/s air stream as shown in the sketch. Estimate (a) the average heat transfer coefficient between air and the fin. (b) the temperature at the end of the fin. (c) the rate of heat flow from the fin with glycerol at 20°C flowing over the fin at 2 m/s. The plate temperature is 50°C.
GIVEN
• A stainless steel pin fin in an air stream
• Pin length (L) = 5 cm = 0.05 m
• Pin diameter (D) = 6 mm = 0.006 m
• Glycerol velocity (U?) = 2 m/s
• Glycerol temperature (T?) = 20°C
• Plate temperature (Tp) = 50°C FIND
(a) The average heat transfer coefficient ( h c) (b) The temperature of the end of the fin (TL) (c) The rate of heat flow from the fin (qf) ASSUMPTIONS
• Steady state
• Turbulence in the glycerol approaching the fin is low
• Radiative heat transfer is negligible
• Steel is type 304
• Steel properties are uniform
• Variation of the thermal properties of glycerol and steel with temperature is negligible
PROPERTIES AND CONSTANTS
Thermal conductivity (k) = 0.285 W/(m K) Kinematic viscosity (?) = 1175 × 10–6 m2/s Prandtl number (Pr) = 12,609 for type 304 stainless steel ks = 14.4 W/(m K) at 20°C
Match the words at the left to the correct blanks in the sentences at right. Use each choice only once.
A. Spacecraft images show fountains of ice spraying into space from Saturn's moon _________ B. Jupiter has three moons for which there is evidence of a global, subsurface ocean of liquid water, with the strongest evidence favoring an ocean on _________ C. ______ is the most volcanically active world in the solar system. D. Scientists have detected lakes of liquid methane and ethane on the surface of __________ E. The two moons that are larger than the planet Mercury are Titan and __________, which is also the largest of Jupiter's moons (and largest moon in the solar system).