When does a protostar become a true star?
A) when the star is 1 million years old
B) when the central temperature reaches 1 million Kelvin
C) when nuclear fusion begins in the core
D) when the thermal energy becomes trapped in the center
E) when the stellar winds and jets blow away the surrounding material
C
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2.9×10^7 is the same as
a. 2.9 thousand. b. 29 thousand. c. 290 thousand. d. 2.9 million. e. 29 million.
The one term of the Drake equation whose value remains completely unknown is the average lifetime of a technological civilization
Indicate whether the statement is true or false
A grating has 450 lines per millimeter. What is the highest order m that contains the entire visible spectrum from 400 nm to 700 nm?
A) m = 2 B) m = 3 C) m = 4 D) m = 5 E) m = 6
Three solid, uniform, cylindrical flywheels, each of mass 65.0 kg and radius 1.47 m, rotate independently around a common axis through their centers
Two of the flywheels rotate in one direction at 8.94 rad/s, but the other one rotates in the opposite direction at 3.42 rad/s. Calculate the magnitude of the net angular momentum of the system. A) 1020 kg ? m2/s B) 1500 kg ? m2/s C) 975 kg ? m2/s D) 940 kg ? m2/s