Essential Physics: Sample Chapter 3
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The language of physics: motion


Physics uses specific meanings for words that may be used differently in conversation. You may be familiar with the following physics terms through things you learned before or from your own, everyday experiences. Below are different ways of describing each term in everyday usage.
speed How fast or slow, what the speedometer in your car reads, distance divided by time, miles per hour, kilometers per hour
distance The space between two points; how far away something is; a measurement of length, height, meters, centimeters, feet, or inches
position Where you are, the place occupied by a piece on a game board, a location on a map
origin
 
The place you start, the beginning, the reference point, (0, 0)
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Different ways of visualizing motion
Some physics terms are related to words used in conversation, but have deeper and more defined meanings in physics. These terms make talking about physics more accurate because the terms have very specific meanings. Below are ways of describing these terms along with examples for each.
velocity Speed with direction, 4 m/s east, 55 mph north, positive and negative speed
displacement A movement between two points, a change in position that can be positive or negative, 30 m south
coordinates The numbers that identify a specific place, (x, y) or (x, y, z), 30 km north and 8 km east, (8, 30) km
vector
 
A quantity that includes information about direction, 100 km north
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Velocity versus time graph for Carmina's driving tripGraphs tell stories of how things change over time. Here is an example that might have produced the graph on the right.

Carmina drove through traffic for half an hour. Then traffic cleared and she drove at 60 km/hr for 30 min to reach a park in time to meet a friend. After staying for half an hour, Carmina drove home at 40 km/hr since traffic was light and she was in no hurry.

Can you identify five ways in which the story matches the graph? Read the text aloud

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