Problem:

Q: What force holds planets in their orbits?   A:
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A: gravity


Problem:

Q: According to early accounts, newton was inspired to make the connection between falling bodies and astronomical motions when he saw an apple fall from a tree and realized that if the gravitational force could extend above the ground to a tree, it might also reach this?   A:
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A: sun


Problem:

Q: An solid object with an irregular shape can be measured via what method?   A:
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A: displacement


Problem:

Q: What is water vapor density known as?   A:
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A:
humidity