How does the density wave theory explain the presence of young stars in the spiral arms?
What will be an ideal response?
Spiral arms are dynamically stable regions of compression that move slowly around the galaxy. Gas clouds moving at orbital velocity around the galaxy overtake the slow-moving arms from behind and slam into the gas already in the arms. The sudden compression of the gas can trigger the collapse of the gas clouds and the formation of new stars. Newly formed stars and the remaining gas eventually move on through the arm and emerge from the front of the slow-moving arm to resume their travels around the galaxy.
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Surrounding every stationary electron is
A) a magnetic field. B) an electric field. C) both of these D) neither of these
A steady horizontal force lasting for 2.1 s gives a 1.25 kg object an acceleration of 3.2 m/s2 on a frictionless table. What impulse does this force give to the object?
A) 11 kg ? m/s B) 26 kg ? m/s C) 2.6 kg ? m/s D) 8.4 kg ? m/s
How much kinetic energy must a deuterium ion (charge 1.6 × 10^?19 C) have to approach to within 10?14 m of another deuterium ion? (1 MeV = 1.6 × 10^?13 J)
What is the maximum velocity of a photoelectron emitted from a surface with work function 5.22 eV when illuminated by 200-nm ultraviolet light? (melectron = 9.11 × 10^-31 kg, h = 6.63 × 10^-34 J×s, 1 eV = 1.60 × 10^-19 J, and 1 nm = 10-9 m)
a. 800,000 m/s c. 653,000 m/s b. 212,000 m/s d. 591,000 m/s