MOTION

        
    AND  
     

PHYSICS
Definitions Graphs Equations Quiz What to Watch For!
       
       
       
       
DEFINITIONS:  
  • Kinematics
 The area of physics that studies motion but not what causes the motion.
  • Position
 Where you are relative to a designated point or origin or the PRODUCT of Velocity and time.
  • Dispacement
 Change in position. (This may not give the same value as distance* moved)
  • Velocity
 Change in position divided by change in time: a RATIO
  • Acceleration
 Change in velocity divided by change in time: a RATIO
  • *Distance
 The length of the path taken between two points
  • *Speed
 Distance divided by time (may not give the same value as velocity)

 

GRAPHS
Remember that ------- vs -------- means "y" vs "x" or "dependent" vs "independent variable.
  • Position vs Time

The slope of this graph gives us a RATIO that is velocity! There are 2 types of slopes to watch for.

1

  1. The slope of the line that connects the point at the start of a period of time to the point at the end of a period of time. This slope is called AVERAGE VELOCITY.

  2. The slope of the tangent drawn at one        point in time is called        INSTANTANEOUS VELOCITY.

 
  • VELOCITY vs TIME 

The slope of this graph gives us a RATIO that is acceleration! Once again there are 2 types of slopes to watch for. The same rules apply to AVERAGE ACCELERATION and to INSTANTANEOUS ACCELERATION!
 
But things are more complicated now-- you can use this graph to find two things depending on whether you calculate the SLOPE (RATIO) or PRODUCT (AREA)

     

 Change in velocity divided by change in time: a RATIO or a SLOPE ONLY for the graph of velcoity vs time produces acceleration!

     

 Velocity multiplied by time produces CHANGE IN POSITION: a Product or the AREA between the graph line and the axis ONLY for the graph of velocity vs time!

 
Try this for visualizing motion !

 

EQUATIONS:  
  • Average Velocity
 v = Dx/ Dt     (or for constant acceleration ONLY avg  V=   (vo + vf) / 2)
  • Instantaneous Velocity
 limit as Dt approaches 0 for the ratio Dx/ Dt    (or the derivative of positon as a function of time)
  • Average Acceleration
 a = Dv/ Dt
  • Instantaneous Acceleration
 limit as Dt approaches 0 for the ratio Dv/ Dt    (or the derivative of velocity as a function of time)
  • Position in terms of time
 Dx = V0t+ 1/2 at2
  • Position without time
 2aDx= Vf2-V02