Motion Diagrams

Motion diagrams are a pictorial description of an object in motion.  They show an object's position and velocity at the start, end, and several spots in the middle, along with acceleration (if any). Click on the links to the right of the diagram to see different motions and the associated diagram.

Constant Right
Constant Left
Speeding up Right
Speeding up Left
Slowing down Right
Start from rest
Coming to a stop

Steps for making a motion diagram:

  1. Draw a box or a dot representing the object at the start and end of the time of interest.
  2. Draw a box or a dot representing the object at two or three equally spaced intermediate times.  If the object is traveling at a constant rate, these will be equally spaced.  If it is speeding up, they will get progressively further apart.  If it is slowing down, they will get progressively closer together.
  3. Draw a vector (arrow) over each box representing the velocity at that point.  The vector will point in the direction of motion and its length will represent the relative speed of the object at that point.  Label these vectors "V."
  4. If the object is speeding up or slowing down, draw another vector above them representing the acceleration.  The acceleration will be proportional to the difference between a velocity vector and the one previous to it in time; it will point in the same direction as the V vectors if the object is speeding up and the opposite direction if it is slowing down.
  5. If the object turns around and comes back, you may want to make two motion diagrams for clarity; one from the start until the point that the object turns around, and the other from the point it turns around to the end.
Exercise created by Scott Bonham, Western Kentucky University.
Physlet by Wolfgang Christian, Davidson College