A heat pump takes in energy from a 250 K thermal reservoir outside a house and discharges 140 J of energy into a 350 K thermal reservoir inside a house. What is the minimum amount of work needed to make the pump work?
A. 67.0 J
B. 50.0 J
C. 40.0 J
D. 37.0 J
C. 40.0 J
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____ galaxies have a great many short spiral segments branching from the spiral arms
a. Grand design b. Super spiral c. Cepheid d. RR Lyra e. Flocculent
Suppose we had a device that allowed us to see Earth's interior. If we looked at a typical region of the mantle, what would we see happening?
A) not much—on human time scales, the mantle looks like solid rock B) hot molten rock rising upward throughout the mantle and cool, solid rock falling downward C) a rapid, up-and-down churning of the material in the mantle D) dense metals falling downward while low-density rock rises upward
When a sine wave is used to represent a sound wave, the crest corresponds to
a. rarefaction. b. condensation. c. point where molecules vibrate at a right angle to the direction of wave travel. d. region of low elasticity.
An 8 000-kg aluminum flagpole 100-m high is heated by the sun from a temperature of 10°C to 20°C. Find the increase in internal energy (in J) of the aluminum. (The coefficient of linear expansion is 24 × 10^?6 (°C)?1, the density is 2.7 × 10^3 kg/m3, and the specific heat of aluminum is 0.215 cal/g/°C.)
a. 7.2 × 10^5 b. 7.2 × 10^7 c. 7.2 × 10^3 d. 7.2 × 10^1 e. 7.2 × 10^2