A star's luminosity tells us
A) how much energy a star produces.
B) its surface temperature.
C) its rotational speed.
D) both how much energy it produces and its surface temperature.
Answer: A
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A 0.14-km wide river flows with a uniform speed of 4.0 m/s toward the east. It takes 20 s for a boat to cross the river to a point directly north of its departure point on the south bank. What is the speed of the boat relative to the water?
a. 5.7 m/s b. 8.5 m/s c. 8.1 m/s d. 7.0 m/s e. 6.4 m/s
What is the difference between parallel and counter flow?
What will be an ideal response?
A 60-?C charge is held fixed at the origin and a ?20-?C charge is held fixed on the x axis at a point x = 1.0 m. If a 10-?C charge is released from rest at a point x = 40 cm, what is its kinetic energy the instant it passes the point x = 70 cm?
A. 9.8 J B. 7.8 J C. 8.8 J D. 6.9 J E. 2.8 J
A sample of an ideal gas is slowly compressed to one-half its original volume with no change in temperature. What happens to the average speed of the molecules in the sample?
A) It does not change. B) It becomes 4 times as great. C) It becomes 2 times as great. D) It becomes 1/2 as great. E) It becomes 1/4 as great.