Which event marks the birth of a star?
A) Formation of the planetary nebula
B) Fusion of hydrogen atoms into helium atoms
C) Collapse of an interstellar cloud
D) Formation of a photosphere
E) Instability in an interstellar cloud
B
You might also like to view...
A 15-?F capacitor and a 30-?F capacitor are connected in series, and charged to a potential difference of 50 V. What is the resulting charge on the 30-?F capacitor?
a. 0.70 mC b. 0.80 mC c. 0.50 mC d. 0.60 mC e. 0.40 mC
A train starts from rest and accelerates uniformly until it has traveled 5.6 km and acquired a forward velocity of The train then moves at a constant velocity of for 420 s. The train then slows down uniformly at until it is brought to a halt
The acceleration during the first 5.6 km of travel is closest to which of the following? A) 0.16 m/s^2 B) 0.14 m/ s^2 C) 0.17 m/ s^2 D) 0.19 m/ s^2 E) 0.20 m/ s^2
Two radioactive isotopes, X and Y, both decay to stable products. The half-life of X is about a day, while that of Y is about a week
Suppose a radioactive sample consists of a mixture of these two nuclides. If the mixture is such that the activities arising from X and Y are initially equal, then a few days later the activity of the sample will be due A) predominantly to Y. B) to X and Y equally. C) predominantly to X. D) entirely to Y.
A cast iron pipe (L 5 12 m, weight density 5 72 kN/m3, d2 5 100 mm, and d1 5 75 mm) is lifted by a hoist. The lift points are 6 m apart. The maximum bending stress in the pipe is approximately:
(A) 28 MPa
(B) 33 MPa
(C) 47 MPa
(D) 59 MPa