A layer of insulating material with thermal conductivity K is placed on a layer of another material of thermal conductivity 2K. The layers have equal thickness. What is the effective thermal conductivity of the composite sheet?
A) 1.5K
B) 3K
C) K/3
D) 2K/3
E) K/5
D
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When a ball is thrown straight up, the acceleration at its highest point is
A) upward. B) downward. C) zero. D) horizontal. E) minimum.
Two cars, one in front of the other, are traveling down the highway at 25 m/s. The car behind sounds its horn, which has a frequency of 540 Hz. What is the frequency heard by the driver of the lead car? (vsound = 340 m/s)
a. 463 Hz c. 579 Hz b. 540 Hz d. 500 Hz
An ambulance is generating a siren sound at a frequency of 2,000 Hz. The velocity of sound is 345.0 m/s. The observer and the ambulance are traveling toward each other at a velocity of 24.00 m/s. If the observer is stationary, what is the frequency of the siren perceived by the observer?
A. 2,032 Hz B. 2,150 Hz C. 2,220 Hz D. 2,575 Hz E. 2,750 Hz
Galileo hypothesized that a ball rolling along a flat surface with no change in speed would ________.
A. have no net force acting on it B. slow down as it rolled down a slope C. speed up as it rolled up a slope D. accelerate, depending on its mass E. have a net force acting on it, upward from the surface