What evidence is there that supernovae really have occurred?
A) Crab Nebula
B) supernova remnants
C) existence of heavy radioactive elements in nature
D) observations of the actual explosions
E) All of the above.
E
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Snell's Law: A plastic cube is immersed in water having an index of refraction of 1.33. A laser beam in the plastic strikes the interface at an angle of 14.5° with the normal in the plastic. In the water, this beam makes an angle of 21.8° with the normal. What is the speed of light in the plastic cube? (c = 3.0 × 108 m/s)
Fill in the blank(s) with the appropriate word(s).
This photograph shows a small portion of the Sun's photosphere. What is going on in the bright regions (such as the bright region indicated by the arrow)?
A) Hot gas is rising up from the solar interior. B) Cool gas is falling back down into the solar interior. C) The bright spots are regions of unusually intense magnetic fields. D) The bright spots are what we call sunspots.
A rock from a volcanic eruption is launched straight up. Which one of the following statements about this rock while it is in the air is correct if you neglect the presence of air?
A) On the way up, its acceleration is downward and its velocity is upward, and at the highest point both its velocity and acceleration are zero. B) On the way down, both its velocity and acceleration are downward, and at the highest point both its velocity and acceleration are zero. C) Throughout the motion, the acceleration is downward, and the velocity is always in the same direction as the acceleration. D) The acceleration is downward at all points in the motion. E) The acceleration is downward at all points in the motion except that is zero at the highest point.
Two identical 7-kg bowling balls roll toward each other. The one on the left is moving at +4 m/s while the one on the right is moving at ?4 m/s. What is the velocity of each ball after they collide elastically?
a. Neither is moving. b. ?4 m/s, +4 m/s c. +4 m/s, ?4 m/s d. ?14 m/s, +14 m/s e. +14 m/s, –14 m/s