About what percentage of a star's total lifetime is spent on the main sequence?
A) 10%
B) 20%
C) 50%
D) 90%
E) 100%
D) 90%
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An airplane is flying through a thundercloud at a height of 2 500 m. (This is a very dangerous thing to do because of updrafts, turbulence, and the possibility of electric discharge.) If there is a charge concentration of +42 C at height 4 000 m within the cloud and ?42 C at height 500 m, what is the magnitude of the electric field E at the aircraft? (ke = 8.99 × 10^9 N·m2/C2)
a. 9.4E+4 N/C b. 1.7E+5 N/C c. 6.2E+4 N/C d. 2.6E+5 N/C e. 1.9E+5 N/C
A series circuit consists of ac source, a 90-? resistor, a 0.80-H inductor, and an 80-?F capacitor
The frequency of the source is adjusted so that the capacitive reactance is equal to twice the inductive reactance. What is the frequency of the source? A) 14 Hz B) 13 Hz C) 16 Hz D) 17 Hz E) 19 Hz
You observe a full Moon rising at sunset. What will you see at midnight?
A) a full Moon high in the sky B) a first quarter Moon C) a waning gibbous Moon D) a third quarter Moon