What law explains why a collapsing cloud usually forms a protostellar disk around a protostar?
A) conservation of angular momentum
B) Kepler's third law
C) the universal law of gravitation
D) Wein's law
A) conservation of angular momentum
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Electron Speed: Given that the speed of an electron in the ground state of hydrogen is 2190 km/s, what is the speed of an electron in the n = 4 orbit of hydrogen?
A. 547 km/s B. 31,000 km/s C. 139 km/s D. 178 km/s E. 2180 km/s
Thermal Expansion: The coefficient of linear expansion of copper is 17 × 10-6 K-1 and that of steel is 12 × 10-6 K-1. At 12°C a steel rod has a diameter of 2.540 cm and a copper pipe has a diameter of 2.536 cm. Which one of the following quantities is closest to the temperature to which the copper pipe must be heated in order for the unheated steel rod to fit snugly in the copper pipe?
A. 53°C B. 81°C C. 93°C D. 105°C E. 143°C
Two infinite parallel surfaces carry uniform charge densities of 0.20 nC/m2 and ?0.60 nC/m2 . What is the magnitude of the electric field at a point between the two surfaces?
a. 34 N/C b. 23 N/C c. 45 N/C d. 17 N/C e. 90 N/C
At the end of the Paleozoic era, all
A) dinosaurs became extinct. B) flowering plants grew to great heights. C) fish species became extinct. D) trilobites became extinct.