The four seasons—spring, summer, fall, and winter—are caused by the Sun's changing its daily altitude over a period of 1 year. The Sun's altitude changes
a. simply because Earth revolves eastward about the Sun.
b. simply because Earth rotates on its axis.
c. simply because Earth's axis is tilted 23.5° from the normal to the ecliptic plane.
d. because of the combined effects of (A) and (C).
d
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What is the average value of the magnitude of the Poynting vector at 1 meter from a 100-watt lightbulb radiating in all directions?
a. 1 W/m2 b. 4 W/m2 c. 2 W/m2 d. 8 W/m2 e. 12 W/m2
Distilled water at 75ºF is suddenly exposed to oxygen gas at 75ºF. Determine the time before the oxygen concentration in the water is 0.1% by mass at a point 0.05 inches below the surface of the distilled water.
What will be an ideal response?
A 1500-W heater is connected to a 120-V line for 2.0 hours. How much heat energy is produced?
A) 11 MJ B) 3.0 kJ C) 0.18 MJ D) 1.5 kJ
The force that holds the nucleus together is
A. gravitational force. B. electromagnetic force. C. weak interaction. D. strong nuclear force.