Center of Mass: A 2.0-m rope is lying on a table. You pick up one end and start raising it vertically. How high above the table is the center of mass (or center of gravity) of the rope when half of the rope has lifted off the table?
A. 0.25 m
B. 0.50 m
C. 0.75 m
D. 1.0 m
E. 1.5 m
Answer: A
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A single slit is illuminated at normal incidence with a parallel beam of light having a wavelength of The entire central band of the diffraction pattern is observed at ±90°
The illumination is now replaced by a nonrelativistic beam of electrons, each having a kinetic energy of 980 eV. When this beam hits the slit at normal incidence, at what angle will the first minimum of the electron diffraction pattern occur? (h = 6.626 × 10-34 J ? s, mel = 9.11 × 10-31 kg, 1 eV = 1.60 × 10-19 J) A) 0.095 mrad B) 0.071 mrad C) 0.046 mrad D) 0.12 mrad E) 0.14 mrad
Refracting Telescope: A refracting telescope has a magnification M. If the focal length of the objective lens is doubled and the eyepiece focal length is halved, what is the new magnification?
A. 4M B. 2M C. M/2 D. M/4 E. M
How do we know that there is much more mass in the halo of our galaxy than in the disk?
A) There are so many globular clusters in the halo that their total mass is greater than the mass of stars in the disk. B) Stars and gas clouds in the outskirts of the Milky Way orbit the galaxy at much higher speeds than we would expect if all the mass were concentrated in the disk. C) We have discovered that the halo is filled with an enormous number of brown dwarfs that have a combined mass much greater than the disk. D) Laboratory experiments have proven that the halo must be full of subatomic dark matter particles.
The maximum value of the magnetic field component of an electromagnetic wave is 2.81 ?T. What is the rms value of the magnetic field?
A) 2.81 ?T B) 2.46 ?T C) 3.12 ?T D) 3.97 ?T E) 1.99 ?T