·      Distance: How far an object moves

·      Displacement: Distance and direction from the starting point

o    Example: You run 30 m east, then 20 m west.  Picture it!

o    Answer: Distance = 50 m; Displacement = 10 m east

 

·      Speed: the distance an object travels per unit time

·      Calculating speed:   speed = distance/time  or  s = d/t    

o    Example: If you go 40km in 2 h, what was your speed?

o    Answer: s = d/t = 40km/2h = 20 km/h (remember units!)

o    Constant speed: not slowing down or speeding up

·      Average speed: total distance divided by total time of travel

·      Instantaneous speed: speed at a given moment in time

o    Example: You’re driving from Rio to La Joya.  First you go 65mph, then 45mph, then 55mph, then 30mph.  You went 25 miles in ½ h, so your average speed was 50mph, but your instantaneous speed kept changing.  

·      Velocity: speed and direction of motion

o    Example: 20 km/h east

o    Velocity changes whenever speed or direction changes

 

·      Distance-time graphs are used to show changing motion

·      X = time, Y = distance

·      Flat line: no motion

·      Steep line: fast motion