An isolated air-filled parallel-plate capacitor that is no longer connected to anything has been charged up to Q = 2.9 nC. The separation between the plates initially is 1.20 mm, and for this separation the capacitance is 31 pF
Calculate the work that must be done to pull the plates apart until their separation becomes 5.30 mm, if the charge on the plates remains constant. (?0 = 8.85 × 10-12 C2/N • m2 )
0.46 µJ
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Water entering a shell-and-tube heat exchanger at 35°C is to be heated to 75°C by an oil. The oil enters at 110°C and leaves at 75°C. The heat exchanger is arranged for counterflow with the water making one shell pass and the oil two tube passes. If the water flow rate is 68 kg per minute and the overall heat transfer coefficient is estimated from Table 10.1 to be 320 W/(m2 K), calculate the required heat exchanger area.
GIVEN
• One shell pass, two tube passes counterflow heat exchanger with water in shell, oil in tube
• Water temperatures Tw,in = 35°C Tw,out = 75°C
• Oil temperatures To,in = 110°C Tw,out = 75°C
• Water flow rate m n= 68 kg/min = 1.133 kg/s
• Overall heat transfer coefficient (U) = 320 W/(m2 K)
FIND
• The required area (A)
SKETCH
PROPERTIES AND CONSTANTS
the specific heat of water at the average temperature of 55°C (cpw)= 4180 J/(kg K)
A rectangular wooden block measures 10.0 cm × 4.00 cm × 2.00 cm. When the block is placed in water, it floats horizontally, with its bottom face 1.65 cm below the surface. What is the density of the wood? The density of water is 1.00 g/cm3
A) 0.606 g/cm3 B) 1.65 g/cm3 C) 1.21 g/cm3 D) 0.350 g/cm3 E) 0.825 g/cm3
Our solar system is located about 27,000 light-years from the galactic center. About how far does our solar system travel in one orbit?
A) 54,000 light-years B) 85,000 light-years C) 100,000 light-years D) 170,000 light-years