What color is an H I region?
A) red from ionized hydrogen's alpha transition, such as in the Orion Nebula
B) red from reddening due to dust
C) colorless; it emits in the radio region
D) blue from the scattering of light off the tiny atoms, such as around the Pleiades
E) blue from ionized helium's alpha transition, such as the Horsehead Nebula
C
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Estimation: A reasonable estimate for the height of the walls in an ordinary American home is
A. 10 m. B. 8 m. C. 2.5 m. D. 1.5 m.
A wave travels at 175 m/s along the x-axis. If the period of the periodic vibrations of the wave is 3.00 milliseconds, then what is the wavelength of the wave?
A. 25.5 cm B. 35.6 cm C. 42.9 cm D. 49.5 cm E. 52.5 cm
A thin cylindrical shell is released from rest and rolls without slipping down an inclined plane that makes an angle of 30° with the horizontal. How long does it take it to travel 3.1 m?
A) 1.4 s B) 1.1 s C) 2.1 s D) 1.6 s E) 1.8 s
A 12,000-N car is raised using a hydraulic lift, which consists of a U-tube with arms of unequal areas, filled with incompressible oil and capped at both ends with tight-fitting pistons
The wider arm of the U-tube has a radius of 18.0 cm and the narrower arm has a radius of 5.00 cm. The car rests on the piston on the wider arm of the U-tube. The pistons are initially at the same level. What is the initial force that must be applied to the smaller piston in order to start lifting the car? (For purposes of this problem, you can neglect the weight of the pistons.) A) 727 N B) 926 N C) 2900 N D) 3330 N E) 1.20 kN