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Free-Body Diagrams: Helpers or Muddlers?

Grade Level- 9

Lesson Plan

State Standards:

Essential Question:

Lesson Question:

Are free-body diagrams (FBD) helpful or confusing when solving problems involving motion, displacement and forces? Do they help you organize your thoughts or muddle your brain?


How are the quantities of motion, displacement and forces best represented? Remember these quantities all have a size and a direction. Pictures, words, mathematical equations and vectors can be used. Motion, displacement and forces are vector quantities. Vectors have been used since the 19th century in mathematics and physics. Vectors are arrows labeled with a magnitude (size), and are the most important part of free-body diagrams. At first glance, some free-body diagrams look confusing. Find out if free-body diagrams are helpers or muddlers in solving problems. They can be used as visual representations to help solve a problem or help students better understand the way motion, displacement and forces (vector quantities) work.


Day 1, 2 and 3: Use your notebook as indicated in the procedure steps during specific tasks.

Lesson Experiences:

Process- (include all steps of the lesson procedure -- include instructions for using digital media):


computer - links to web-sites listed under Resources
handout to be filled in


You will have a better understanding of free-body diagrams. You will have created a free-body diagram that represents a problem in in motion and forces. You will find out if free-body diagrams are helpers or muddlers in solving problems. And finally, you may find that drawing vectors and free-body diagrams are not just another task or mechanical procedure, but are useful representations that show how motion, displacement and forces work.


  1. Correctly distinguish between vectors and scalars using items and situations found in class
  2. Notebook content
  3. Creation of a free-body diagram with a vector quantity problem.
  4. Draw your FBD on a vector graphics web-site .


1. On-line Quiz at home
Using Quizlet, distinguish between scalar and vector quantities; identify scenarios that use vectors and free-body diagrams
view the flash cards and one other study option (learn, speller);
play a game (scatter or space race);
take the quiz.

2. Answering follow-up questions on web-sites about FBD's.


You will be able to... Srong Adequate Inadequate


Distinguish between vector and scalar quantities
(identified/demonstrated in class)
All Identified most identified <half  
Notebook Content all entries most entries <half  
Create and use an FBD to solve problem in the handout Both: an FBD with 4 vectors labeled and
corresponding description and problem
Both: an FBD with 4 vectors labeled and
corresponding description and problem
FBD with 2-3 vectors,
brief description but no problem
Design your FBD on a vector graphics web-site. Your FBD done on inkscape in class n/a not done  



On-Line Resources: Research

Web-based software: An Interactive Activity

You Tube Videos

On-Line Resources: Self Assessment

Web-based graphic/drawing tools
Janvas Interactive Graphics


Physical Science 2.4d - Displacement Vectors
Drawing Free Body Diagrams for One Dimensional Motion-Google

Teacher Notes:


D. Rosengrant, A. Van Heuvelen and E. Etkina, Do students use and understand free-body diagrams? 2009 Physics Education Research 5, American Physical Society.