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Kinematics Notes.notebook
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February 19, 2020
Kinematics1D Motion
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Physics the science of matter and energy and of interactions between the two.
Areas of Study in Physical Science1. Kinematics how things move predictive2. Dynamics why things move forces3. Energy 4. Sound5. Light
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Why are they different?
Numbers in Science error from measurement+/ indication direction
Numbers in Mathexact+/ indicate how far from zero
Error in Measurement
1. Human Error
2. Mechanical Error
Demonstration Stop watch measurement
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Who won the race?http://s3uswest2.amazonaws.com/dmvideos.org/players/skaters/skaters.html
1. Who won the race?
2. Why did you say they won the race?
So...who really won the race? How do we decide?
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Motion1. Translational (x, y, z coordinates)2. Rotational3. Vibrational
Kinematics The branch of physics that studies the motion of an object
Translational1. One dimensional2. Two dimensional3. Three dimensional
One Dimensional Motion1. Mathematically2. Motion Diagram (Number Line)3. Graphically (XY graph)
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Motion Diagram (Number Line)
Example B change walking speed/direction
Distance = Displacement =
Pick the origin completely arbitraryPick a time interval completely arbitrary
Example A slow steady walk
Distance = Displacement =
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Scalar QuantityMagnitude only
Distance total length traveledno positive or negative
Speed
Vector QuantityMagnitude and Direction (+/, L/R, N/S/E/W)
Displacement position and direction from starting position.
VelocityAcceleration
Physics Concepts
Physics Equations
Scalar Vector
Average speed or velocity data gathered over a period of time
Instantaneous speed or velocity data for one point in time
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A car travels 145 miles in 80 minutes. Determine the cars average speed in miles per hour.
A car has a velocity of 45 miles per hour north and travels for 35 minutes.Determine the cars displacement in miles.
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A car is traveling at 65 miles per hour. Is this speed or velocity? Instaneous or average? How long (in minutes) does it take to go 200. miles?
A student paces by walking the following path8 ft west in 5 seconds5 ft east in 25 seconds10 ft west in 30 seconds
Calculate the
Distance =
Speed =
Displacement =
Velocity =
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Motion Diagram
What does slope indicate?
How do you know there is a change in direction?
How do you know there is a different velocity/speed?
Motion Diagram
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Position vs Time Graph
Things you should be able to understand or calculate.Average velocity (slope)Average SpeedPositionChanging direction
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Describe the motion of the object over the ten seconds.
Determine the position of the object at 8 seconds.
Determine the position of the object at 4 seconds.
Determine the time the object is at 6 meters.
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Determine the average speed of the object over the entire ten seconds.
Determine the average velocity of the object over the first five seconds.
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Determine the position of the object at 2 seconds.
Determine the position of the object at 7 seconds.
Determine the time the object is at 1 meters.
Determine the time(s) the object changes direction.
Describe the motion of the object over the entire eight seconds.
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Determine the average velocity of the object over the entire eight seconds.
Determine the average velocity of the object over the first five seconds.
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Determine the average speed of the object over the first three seconds.
Determine the average speed of the object over the entire eight seconds.
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Acceleration
The rate at which velocity changes
Can be an:
increase in velocity
decrease in velocity
change in direction
Equation for Acceleration:
In your car we call the gas pedal "the accelerator". What other parts of your car are an accelerator?
Units of acceleration:m/s2
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Practice Problems:
1. A car is moving at the following velocity. Calculate its acceleration.
2. A skydiver accelerates from 40 m/s to 20 m/s in 2 seconds. What is the skydiver’s average acceleration?
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3. A cart rolling down a ramp has an acceleration of 10m/s2 . The cart took 1.5s to travel down the ramp. What is the cart's change in velocity?
4. A cart on a roller coaster is coasting to the top of an incline. The cart's begins its climb at 40m/s and ends at 5m/s. The cart's acceleration was 10m/s/s. How long did it take the cart to reach the top of the incline?
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Velocity vs. Time graphs
Describe the motion of this object.
What does the slope of this line indicate?
Calculate the average acceleration of this object.
Describe the motion of this object.
What does the slope of this line indicate?
Calculate the average acceleration of this object.
