A camera lens has a focal length of 50.0 mm and an aperture setting of f/4.00. What is the diameter of the aperture of this lens?
A) 35.4 mm B) 200 mm C) 12.5 mm D) 10.1 mm E) 25.0 mm
C
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Which of the following is not a piece of evidence supporting the conclusion that active galactic nuclei are powered by accretion disks around supermassive black holes?
A) Observed radiation from the galactic center varies significantly in brightness in times as short as a few days. B) Infrared observations show that many stars are forming near the centers of active galaxies. C) Radio observations sometimes show long jets of material extending millions of light-years out from the galactic center. D) The total amount of radiation coming from the galactic center is, in some cases, comparable to the amount of radiation put out by 10 billion or more ordinary stars. E) Spectral lines from the galactic center indicate that clouds of gas are orbiting a central object at very high speed.
A car with bad shocks bounces up and down with a period of 1.51 s after hitting a bump. The car has a mass of 1 600 kg and is supported by four springs of force constant k. What is k for each spring?
a. 6.9E+3 N/m b. 1.7E+3 N/m c. 1.7E+3 N/m d. 3.5E+3 N/m e. 8.2E+2 N/m
Clocks in a moving reference frame, compared to identical clocks in a stationary reference frame, appear to run
A. backward in time. B. slower. C. faster. D. at the same rate.
A 4.0-kg mass on the end of a string rotates in a circular motion on a horizontal frictionless table. The mass has a constant speed of 2.0 m/s and the radius of the circle is 0.80 m. What is the magnitude of the resultant force acting on the mass?
a. 39 N b. 20 N c. 44 N d. 0 N e. 30 N