The first complex life appeared on Earth about 0.5 billion years ago during the
a. Jurassic Period.
b. Mississippian Period.
c. Cambrian Period.
d. Precambrian Period.
e. Neolithic Period.
C
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A shell is launched with a velocity of 100 m/s at an angle of 30.0° above horizontal from a point on a cliff 50.0 m above a level plain below
How far from the base of the cliff does the shell strike the ground? There are no appreciable effects of air, and g = 9.80 m/s2 at the location of the cliff.
If a twin goes on a trip in a high speed rocket ship, when she returns home she will be younger than her twin sister who did not go on the trip because of
a. time dilation b. length contraction c. the equivalence of mass and energy d. the principle of relativity e. none of the above
Which of the following statements about thermal radiation is always true?
A) A hot object emits more radiation per unit surface area than a cool object. B) A cold object produces more total infrared and radio emission per unit surface area than a hot object. C) A hot object produces more total infrared emission than a cooler object. D) All the light emitted by hot object has higher energy than the light emitted by a cooler object.
Which of the following has not been detected around other stars in the Galaxy?
A) a collapsing nebula of gas B) flattened, spinning disks C) jovian planets D) asteroids E) strong stellar winds