# Acceleration

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```					                       Motion
• Position—separation of an object from a fixed
reference point. Is a vector measurement.
– += to the right or up
– - = to the left or down
• Distance—requires no reference point. Is a
scalar measurement.
• Instantaneous position
• Displacement—change in position. Symbolized
as delta d.
Motion
• Motion diagrams—A series of images of a
moving object that records its position
after equal time intervals.
– At rest
– Speeding up
– Slowing down
– Constant speed
• Link to Motion Diagram Applet
• Link to Another Motion Diagram Site
The Particle Model
• Replace an object with a single point at
the center of the body.
– You can use this model effectively if:
• The size of the object is much less than the
distance it moves.
• Internal motions can be ignored.
Coordinate System
• What is your frame of reference?
• Where is zero?
– Origin—zero point.
– You need to keep horizontal and vertical
displacements on separate axes.
– Position/displacement vectors on a motion
diagram.
– Can there be a negative position? Can there
be a negative time?
Velocity

• Average velocity=displacement/time
– + = to the right or up
– - = to the left or down
• Velocity vs. Speed
• Position-time graph
– Slope=average velocity
– Instantaneous velocity=slope of the
tangent line to the point in question.
Position Time Graph
Acceleration
• a=change in velocity over change in time
• Units
• Positive or negative—What do these signs
mean?
• Deceleration
• Average Acceleration
Acceleration
• Velocity vs. Time graph
– Slope=average acceleration
– Slope of the tangent line to the graph=instantaneous
acceleration.
– Area under the curve=the total displacement.
– Velocity/Time Graph Applet
– Velocity/Time, Position/Time, and Acceleration/Time graph
applets
•   Instantaneous Acceleration
•   Uniform or Constant Acceleration
•   Link to PHET Moving Man Simulation
•   Equations
•   Acceleration due to gravity
Velocity Time Graph
Acceleration Due to Gravity
•   Lowercase g
•   -9.8 meters per second squared
•   -32 feet per second squared
•   Sample Problems
Acceleration Equations
•   vf=vI + at
•   Vf2=vi2 + 2ad
•   d=vit +1/2 at2
•   d=1/2(vf + vi)t

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