Two point charges of +20.0 ?C and -8.00 ?C are separated by a distance of 20.0 cm. What is the magnitude of electric field due to these charges at a point midway between them? (k = 1/4??0 = 8.99 × 109 N • m2/C2)
A) 25.2 × 106 N/C directed toward the negative charge
B) 25.2 × 106 N/C directed toward the positive charge
C) 25.2 × 105 N/C directed toward the negative charge
D) 25.2 × 105 N/C directed toward the positive charge
E) 25.2 × 104 N/C directed toward the negative charge
A
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Hot flue gases from a combustion furnace flow through a chimney, which is 7-m-tall and has a hollow cylindrical cross section with inner diameter di = 30 cm and outer diameter do = 50 cm. The flue gases flow with an average temperature of Tg = 300°C and convective heat transfer coefficient of hg = 75 W/(m2 K). The chimney is made of concrete, which has a thermal conductivity of k = 1.4 W/(m K). It is exposed to outside air that has an average temperature of Ta = 25°C and convective heat transfer coefficient of 15 W/(m2 K). For steady-state conditions, (a) determine the inner and outer wall temperatures, (b) plot the temperature distribution along the thickness of the chimney wall, and (c) determine the rate of heat loss to outside air from the chimney. Solve the problem by numerical
analysis using a nodal network with ?r = 2 cm and ?? = 10°.
GIVEN
- Hot flue gas flow in a hollow cylindrical 7-m-tall chimney with inner and outer diameters of
di = 0.3 m and do = 0.5 m, and thermal conductivity k = 1.4 W/(m K).
- Average hot gas temperature Tg = 300°C and heat transfer coefficient
- Outside air average temperature Ta = 25?C and heat transfer coefficient
FIND
- The temperature distribution in chimney wall and the inside and outside wall temperatures.
- Rate of heat loss from gas to outside air through the chimney.
ASSUMPTIONS
- Steady state conditions, and there is no heat generation in the chimney wall and the conduction
along the height of the chimney is negligible.
Energy is released during a nuclear reaction due to a conversion between mass and energy. Mass is not conserved. The initial and final amounts are different. If a total of 1.0 gram of mass is "missing", how much energy has been released?
a. 9.0 × 10^11 J b. 9.0 × 10^17 J c. 9.0 × 10^15 J d. 9.0 × 10^13 J e. 9.0 × 10^16 J
An assault rifle fires an eight-shot burst in 0.40 s. Each bullet has a mass of 7.5 g and a speed of 300 m/s as it leaves the gun. What is the average recoil force on the gun during that burst?
A) 45 N B) 5.6 N C) 16 N D) 2.0 N E) 23 N
The net force always points in the same direction as:
a. the displacement. b. the frictional force. c. the velocity. d. the force of gravity. e. the acceleration.