A thermodynamic engine having the maximum possible efficiency has an efficiency of 25% when operating between two heat reservoirs. If the temperature of the cold reservoir is 300 K, what is the temperature of the hot reservoir?
A) 350 K
B) 375 K
C) 400 K
D) 450 K
E) 500 K
C
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Dr. Chuck projects a ball horizontally from a lab bench. The ball lands on a bullseye marked on the floor a horizontal distance equal to the ball's initial speed
A) multiplied by its time in the air. B) coupled with its speed of fall. C) squared plus its downward speed squared when hitting the floor. D) all of the above E) none of the above
Which is more common: a star blows up as a supernova, or a star forms a planetary nebula/white dwarf system?
A) Supernovae are more common. B) Planetary nebula formation is more common. C) They both occur in about equal numbers. D) It is impossible to say.
You are given two converging lenses to build a compound microscope. Lens A has focal length 0.50 cm and lens B has focal length of 3.0 cm. Which one of the two lenses would you use for the objective?
A) Lens A, because it has the shorter focal length. B) Lens B, because it has the longer focal length. C) It makes no difference which lens I use for the objective. D) None, because the objective should be a diverging lens.
An observer on the Moon looking at Earth would
a. always see a fully illuminated Earth. b. always see a half-illuminated Earth. c. see phases of Earth. d. see continuous darkness.