What evidence do we have that Mars once had a thicker atmosphere?
What will be an ideal response?
Liquid water cannot exist now on the Martian surface because it would boil away in the extremely low atmospheric pressure, so evidence that water once flowed on Mars means that surface conditions there must have been quite different long ago. It must have had a thicker atmosphere.
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Kirchhoff's Rules: For the circuit shown in the figure, write the Kirchhoff loop equation for the entire outside loop. Notice the directions of the currents!
What will be an ideal response?
One 20-year-old twin brother takes a space trip with a speed of 0.80c for 30 years according to a clock on the spaceship. Upon returning to the Earth, what is his own age and the age of the Earth-based twin brother?
A) 20; 30 B) 30; 50 C) 40; 60 D) 50; 70 E) 70; 90
Which answer below is not a statement of the second law of thermodynamics?
a. Real processes proceed in a preferred direction. b. Energy does not flow spontaneously by heat from a cold to a hot reservoir. c. The entropy of the universe increases in all natural processes. d. In theory, heat engines working in a cycle employ reversible processes. e. You cannot construct a heat engine, operating in a cycle that does nothing but take heat from a reservoir and perform an equal amount of work.
When a rainbow is seen as a complete circle from an airplane, the airplane's shadow is
A) in the center of the rainbow. B) in the lower part of the rainbow. C) in the upper part of the rainbow. D) totally outside the rainbow. E) nowhere, for there is no shadow.