Thermodynamic Devices: An ideal Carnot air conditioner operates between an indoor temperature of 20°C and an outdoor temperature of 39°C. How much energy does it use to remove 2000 J of heat from the interior of the house?
A. 105 J
B. 130 J
C. 780 J
D. 520 J
E. 340 J
Answer: B
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If an electron has the same de Broglie wavelength as the wavelength of a 390-nm photon in vacuum,
what is the speed of the electron? (melectron = 9.11 × 10-31 kg, c = 3.0 × 108 m/s, h = 6.626 × 10-34 J ? s) A) 2100 m/s B) 540 m/s C) 1900 m/s D) 1700m/s E) 1500 m/s
A gas consists of particles of mass 3.00 × 10-26 kg. What is the pressure in a gas of these particles if there are 2.00 × 1025 particles per cubic meter of gas and the rms speed of the particles is 400 m/s?
A) 1.01 × 105 N/m2 B) 1.60 × 104 N/m2 C) 9.60 × 104 N/m2 D) 4.80 × 104 N/m2 E) 3.20 × 104 N/m2
A propeller is spun up from rest to 1500 rpm under the influence of a constant torque in 15.0s. If the work done by the engine in giving the propeller its final angular velocity is 25kJ, what is the torque supplied by the engine?
A. 21Nm B. 11 Nm C. 42 Nm D. 21 Nm E. 130 Nm
On a warm day a pool of water transfers energy to the air as heat and freezes. This is a direct violation of:
A. the zeroth law of thermodynamics B. the first law of thermodynamics C. the second law of thermodynamics D. the third law of thermodynamics E. none of the above