Earth has been gradually warming over the past few decades. Based on a great deal of evidence, scientists believe that this warming is caused by
A) the increase in forest fires during recent years.
B) human activities that are increasing the concentration of greenhouse gases in Earth's atmosphere.
C) the human release of chemicals called CFCs into the stratosphere.
D) the fact that our politicians spout a lot of hot air.
B
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TV remote controls use ________ radiation
Fill in the blank(s) with correct word
A chain reaction progresses when the average number of liberated neutrons that cause further fissions is
A) zero. B) less than one. C) one or more. D) none of the above
A ballerina spins initially at 1.5 revolutions/second when her arms are extended. She then draws in her arms to her body and her moment of inertia becomes 0.88 kg-m2 and her angular speed increases to 4.0 rev/s
Determine her initial moment of inertia.
The air in a tube open at both ends is sent into its fundamental resonance. One end of the tube is then closed and the air column is again set into its fundamental resonance. The resonant frequency _____ after the end is closed
a. halves c. doubles b. stays the same d. increases by a factor of 1.4