Equilibrium: A uniform ladder 12 meters long rests against a vertical frictionless wall, as shown in the figure. The ladder weighs 400 N and makes an angle ? = 51° with the floor. A man weighing 874 N climbs slowly up the ladder. When he is 78 m from the bottom of the ladder, it just starts to slip. What is the coefficient of static friction between the floor and the ladder?
Fill in the blank(s) with the appropriate word(s).
0.49
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Thin Films: A 360-nm thick oil film floats on the surface of a pool of water water. The indices of refraction of the oil and the water are 1.5 and 1.33, respectively. When the surface of the oil is illuminated from above at normal incidence with white light, what are the two wavelengths of light between 400 nm to 800 nm wavelength that are most strongly reflected?
A. 410 nm and 700 nm B. 430 nm and 720 nm C. 450 nm and 740 nm D. 470 nm and 760 nm E. 490 nm and 780 nm
The strings in musical instruments that have greater mass tend to produce notes of
A) higher frequency. B) lower frequency. C) the same frequency. D) none of the above
What type of observation can astronomers use to measure the composition of extrasolar planet atmospheres?
A) measurements of the host star's velocity throughout an orbital cycle B) measurement of how frequently the planet blocks the host star's light C) comparisons of spectra when planets are in front of or are eclipsed by their host stars D) combination of a transit observation and a Doppler shift measurement
Although theory says a massive black hole with an accretion disk should be emitting X-rays, many black holes emit
A) mainly in the gamma. B) virtually no radiation at all. C) only in the visible. D) equally across the entire electromagnetic spectrum. E) mostly in the infrared.