unit 2 linear motion - dentonisd.org is relative when we describe something in motion, we are...
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![Page 1: Unit 2 Linear Motion - dentonisd.org is relative When we describe something in motion, we are comparing it to something else. For example: A car is driving 45 miles per hour: You only](https://reader031.vdocuments.us/reader031/viewer/2022022521/5b242cb47f8b9a84658b51af/html5/thumbnails/1.jpg)
Unit 2
Linear Motion
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Kinematics
Kinematics is the study of howthings move, but does not address the question of why they move.
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Dynamics
The study of why things move is called dynamics.
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Therefore, the “general” term for the study of motion (the how and why) is called: MECHANICS
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Motion is relativeWhen we describe something
in motion, we are comparing it to something else.
For example:
A car is driving 45 miles per hour:
You only know it is moving because the road and trees around it are staying still.
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So, for motion to be found, there must be something that is stationary---called a reference point
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SpeedSpeed is a measure of how
fast something is moving.
The speed at any instant is called instantaneous speed.
Average speed = total distancetime interval
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SPEED AND DISTANCE
When you measure speed, it is based on the “TOTAL” distance covered
OR, “how far” an object has traveled in a given amount of time
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Graphs of Motion
You can graph the relationships of both distance and time by using x and y values.
X is independent and Y is dependent
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GRAPHS FOR SPEED
Graph for constant speed---x axis is time in seconds; y axis is distance in meters-
Graph for variable speed ---also called changing speed
Direct relationship graph—X & Y do the same thing.
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Graphs of Motion
As you graph the relationships of both time and distance, so can speed and displacement (position) by using x and y values on a graph
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Remember:
“per’ means “every”
So, 45 miles per hour is saying that something moves a distance of 45 miles EVERY hour
(distance/time)
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What is the speed of a man running 8 miles in 2 hours?
Answer:
8 miles (total distance) / 2 hours (time interval)
8/2 = 4 miles/hour
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Velocity
Velocity is speed in one direction.
Constant velocity IS remaining the same, or CONSTANT.
Changing velocity is NOT remaining the same, or CHANGING.
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TERMS RELATED TO MOTION
Displacement: change in position due to a “difference” in start position and final position
Displacement is used with the term “velocity”
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GRAPHS AND RELATIONS
Direct relationship graphs:
Straight line---x and y axis do the same thing (increase or decrease)
Inverse relationship---x and y axis do the “opposite” of each other ( i.e. x will increase and y will decrease)
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VELOCITY AND DISPLACEMENT
Velocity is a “vector” quantity, therefore it has direction
The main difference between speed & velocity----velocity has direction and displacment
Velocity has displacement (position) which means that there is an “initial or start” point and a “final” point. So, df--final
or di—start or initial point
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Graphs of Motion
The slope of the line in a position (displacement) vstime graph is velocity.
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Graphs for velocity
Velocity can be constant or it can be variable----see example of
Constant velocity
Variable velocity
Note the “y” axis
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position vs time
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time (s)
po
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