What age would radiometric dating give for a chunk of recently solidified lava from Kilauea, an active volcano in Hawaii?
a. zero years
b. the age of Earth
c. the age of the universe
b. the age of the solar system
Ans: a. zero years
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In the process of fluorescence, the input is high-frequency light and the output is
A) higher-frequency light. B) equally high-frequency light. C) lower-frequency light. D) none of the above
Calculate the magnitude of the flux of a constant electric field of 5.00 N/C in the z-direction, through a rectangle with area 4.00 m2 in the xy-plane
1.0 2.10.0 N·m2/C 3.20.0 N·m2/C 4.More information is needed.
Two point charges each experience a 1-N electrostatic force when they are 2 cm apart. If they are moved to a new separation of 8 cm, what is the magnitude of the electric force on each of them?
A) 2 N B) 1/2 N C) 1/4 N D) 1/8 N E) 1/16 N
A thin electronic circuit board, 0.1 m by 0.1 m in size, is to be cooled in air at 25°C. The board is placed in a vertical position and the back side is well insulated. If the heat dissipation is uniform at 200 W/m2, determine the average temperature of the surface of the board cover.
GIVEN
• Vertical circuit board in air
• Back is well insulated
• Board dimensions (L × H) = 0.1 m × 0.1 m
• Air temperature (T ?) = 25°C
• Uniform heat dissipation rate ( q G/A) = 200 W/m2
FIND
• The average temperature of the surface of the board (Ts)
ASSUMPTIONS
• Ambient air is still
• The board has reached steady state
• Radiation is negligible
SKETCH
