An electron (m = 9.1 × 10^?31 kg, q = ?1.6 × 10^?19 C) starts from rest at point A and has a speed of 5.0 × 10^6 m/s at point B. Only electric forces act on it during this motion. Determine the electric potential difference VA ? VB
a. ?71 V
b. +71 V
c. ?26 V
d. +26 V
e. ?140 V
a
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Astrology is an example of _______________
Fill in the blank(s) with correct word
Mathematical models indicate that ___________ galaxies are produced by high-speed collisions in which a smaller galaxy passes through another galaxy almost perpendicular to the disk of the galaxy
a. ring b. spiral c. antenna d. irregular e. tidal tail
Water flowing in a long aluminum tube is to be heated by air flowing perpendicular to the exterior of the tube. The ID of the tube is 1.85 cm and its OD is 2.3 cm. The mass flow rate of the water through the tube is 0.65 kg/s and the temperature of the water in the tube averages 30°C. The free stream velocity and ambient temperature of the air are 10 m/s and 120°C, respectively. Estimate the overall heat transfer coefficient for the heat exchanger using appropriate correlations from previous chapters. State all your assumptions.
GIVEN
• Air flowing perpendicular to the exterior of an aluminum tube with water flowing within the tube
• Tube diameters
? Inside (Di) = 1.85 cm = 0.0185 m
? Outside (Do) = 2.3 cm = 0.023 m
• Mass flow rate of water (mw) = 0.65 kg/s
• Average temperature of the water (Tw) = 30°C
• Air free stream velocity (Va) = 10 m/s
• Air temperature (Ta) = 120°C FIND
• The overall heat transfer coefficient (U)
ASSUMPTIONS
• Steady state
• The variation of the Prandtl number of air with temperature is negligible
• The aluminum is pure
SKETCH
PROPERTIES AND CONSTANTS
thermal conductivity of aluminum (kal) = 238 W/(m K) at 75°C
for water at 30°C
Density (?w) = 996 kg/m3 Thermal conductivity (kw) = 0.615 W/(m K)
Absolute viscosity (?w) = 792 × 10–6 (Ns)/m2
Prandtl number (Prw) = 5.4
for dry air at 120°C
Thermal conductivity (ka) = 0.0320 W/(m K)
Kinematic viscosity (?) = 26.0 × 10–6 m2/s
Prandtl number (Pr) = 0.71
A series RC circuit has a time constant of 0.900 s. The battery has an emf of 24.0 V, and the maximum current in the circuit is 0.500 mA.What is the charge stored in the capacitor 2.00 s after the switch is closed?
a. 401 ?C b. 18.8 ?C c. 108 ?C d. 450 ?C