Galactic collisions ____
a. are very rare, since few galaxies are in clusters
b. will cause stars in each galaxy to collide and trigger supernova events
c. often trigger bursts of star formation
d. only happen in poor clusters
e. usually break large galaxy into several small ones
c
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This graph shows the rotation curves of four different spiral galaxies. Based on these curves, what do all four galaxies have in common?
A) Their most distant stars all orbit at about the same speed as stars located about 30,000 light-years from their centers. B) Their fastest-moving stars are always located within about 1,000 light-years of their centers. C) They all have supermassive black holes near their centers. D) All their stars take about 200 million years to complete a single orbit, no matter how far they are from the galactic center.
At what orientation angle relative to the magnetic field direction does the magnetic potential energy of a magnetic dipole have its largest value?
a) 0° b) 45° c) 90° d) 135° e) 180°
Huyghens claimed that near the surface of the Earth the velocity downwards of an object released from rest, vy, was directly proportional to the square root of the distance it had fallen, 
. This is true if c is equal to
A.
.B.
.C.
D.
.E.
When a 10-N object is suspended at rest by two equally-taut vertical strands of rope, the tension in each strand is
A) less than 5 N. B) 5 N. C) more than 5 N. D) 10 N.