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Definition
| A point against which position is measured |
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| A physical measurement that contains directional information |
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| A physical measurement that does not contain directional information |
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| The time rate of change of an object's velocity |
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| The state of an object that is falling towards the earth with nothing inhibiting its fall |
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| If an object's position does not change relative to a reference point, is it in motion relative to that reference point? |
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Definition
It is not moving relative to the relative to the reference point --
Why? In order for motion to occur, an object's position must change. Since this object position is not changing it is not moving relative to the reference point. |
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| A glass of water sits on a counter. Is it in motion? |
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Definition
The glass of water is moving relative to many reference points.
Why? To someone standing still in the house, the glass is not moving. However, relative to any object not on earth, it is in motion. In fact, if you walk towards the glass, the glass is in motion relative to you, because the glass's position relative to you changes! |
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A child is floating in an inner tube on a still lake. His position does not change. He watches two girls job along the shore of the lake. The girls are keeping perfect pace with each other. Neither is pulling a head of nor falling behind the other.
A. Relative to whom is the child in motion?
b. Relative to whom is the first girl in motion?
c. Relative to whom is the second girl not in motion? |
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Definition
A. The child is in motion relative to the two girls. Even thought the child is sitting still, his position relative to the girls is changing. Thus, he is in motion relative to the girls.
B. The first girl is in motion relative to the child. Since the position of her relative to the child is changing, she is in motion relative to him.
c. The second girl is motionless relative to the first girl. The girls are keeping perfect pace. Thus, their position relative to each other does not change. They are therefore both motionless with respect to each other. |
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| What is the speed of a boat that travels 10 miles in 30 minutes? Answer in miles per hour |
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Definition
This problem gives us distance and time and asks for speed. Thus, we need to use equation example 9.1
answer 20 miles/hour |
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