A concrete wall of a cold storage room measures 3.0 m high, 5.0 m wide, and 20 cm thick. The inside wall is to be covered by a layer of wood in order to reduce the rate of heat flow through the wall by 90 percent
The inner surface of the wooden wall is maintained at -10°C and the outer surface of the concrete wall is at 20°C. The thermal conductivities of concrete and wood are 0.80 W/m ? K (concrete) and 0.040 W/m ? K (wood). What should be the thickness of the layer of wood?
A) 100 mm B) 90 mm C) 60 mm D) 70 mm E) 80 mm
B
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A jet fighter plane is launched from a catapult on an aircraft carrier. It reaches a speed of 42 m/s at the end of the catapult, and this requires 2.0 s. Assuming the acceleration is constant, what is the length of the catapult?
A) 16 m B) 24 m C) 42 m D) 63 m E) 84 m
Which of the following species is the reducing agent?
2 CuBr ? 2Cu + Br2 A) Cu B) CuBr C) Cu+ D) Br- E) Br2
Process of Science: Pluto is no longer considered a planet. Explain the new discoveries that led to this change
What will be an ideal response?
Ralph walks 3 m to the left in 2 seconds, then 4 m to the right in 3 seconds. Next, he stops for 3 seconds, and finally walks 5 m to the left in 4 seconds
Ralph's final position is closest to:
1.0 m 2.2 m 3.4 m 4.6 m 5.8 m 6.10 m 7.12 m 8.14 m 9.The negative of one of the choices above 10.Impossible to determine