Why do stars in the disk of a spiral galaxy orbit in roughly the same direction, in the same plane in space?
A) It is pure coincidence; the stars just happen to be going in the same direction.
B) After the stars formed, gravity pulled the stars down into a plane in space, all orbiting a supermassive black hole.
C) The gas that formed the stars was shaped as a giant, rotating disk.
D) Collisions between the stars caused their motions to organize into a general, spinning disk direction.
C
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The positron is
A) the anti-particle to the proton. B) identical to the neutron but with a positive charge. C) one of the three particles that go together to make a proton. D) only hypothetical at the present time. E) the anti-particle to the electron.
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a. a value greater than 40 ?T b. 40 ?T c. a value less than 40 ?T d. It could be any value.
Two slits are illuminated with green light (l = 540 nm). The slits are 0.05 mm apart and the distance to the screen is 1.5 m. At what distance (in mm) from the central maximum on the screen is the average intensity 50% of the intensity of the central maximum?
a. 1 b. 3 c. 2 d. 4 e. 0.4