The Department of Energy develops a new reversible engine which has a COP of 4 when operated as a refrigerator and a COP of 5 when operated as a heat pump. What is its efficiency when operated as an engine doing work?
A) 10.%
B) 20.%
C) 25.%
D) 45.%
E) 80.%
B
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Resolution: With what color light would you expect to be able to see the finest detail when using a microscope?
A. red, because of its long wavelength B. yellow, because of its intermediate wavelength C. blue, because of its shorter wavelength D. The color does not matter.
A disk is suspended by a nail such that it pivots in a vertical plane about a point on the edge of the disk. If the disk's radius is 25 cm, what is the period of oscillation?
A. 0.71 s B. Need the mass of the disk to calculate the period. C. 1.2 s D. 1.51 s
Are cosmic rays electromagnetic waves? Why or why not?
What will be an ideal response?
A copper cylinder with a mass of 125 g and temperature of 345°C is cooled by dropping it into a glass beaker containing 565 g of water initially at 20.0°C
The mass of the beaker is 50.0 g and the specific heat of the glass is 840 J/kg?K. What is the final equilibrium temperature of the system, assuming the cooling takes place very quickly, so that no energy is lost to the air? The specific heat of copper is 385 J/kg?K and that of water is 4190 J/kg?K.