Using PhET Simulations to Explore the Cause and Effect Relationship between Forces and Motion


One of my goals this year is to develop a third grade forces and motion curriculum with a team of Burlington elementary teachers.  While this work is only in its infancy I am optimistic then at least one of the activities to be built into our scope and sequence will be the use of a PhET Forces & Motion model. Constructed in HTML5 (and therefore usable on our students’ iPads) the tug of war model and friction model provide great opportunity for students to test multiple scenarios using a varied amounts of forces, leading to more opportunities for the students to predict and explain the results of their trials.


Students exploring how forces impact the motion of the candy cart within the HTML5 PhET Forces and Motion model.

An opportunity arose the very first week of school when fourth grade teacher, Todd Stead invited me to come help shake up his “Forces, Motion, and Flight” unit. Mr. Stead gave me additional time beyond the normal 40 minutes to pilot the lesson, which was helpful because it allowed us to setup their notebooks before diving into more fundamental questions like “What is a model?” and make up for some lost time getting all students to the correct URL. Once things got going the classroom was immediately abuzz with students exploring the tug of war model, adding and subtracting red and blue avatars from one side of the rope and the other, running the model frequently, only to pause it mid-way and change the avatars around once again.

I built a lesson around the question, “How do balanced forces affect an object’s motion?” designed to integrate the following elements from the NGSS (and new Massachusetts standards.)

  • Develop and/or use models to describe and/or predict phenomena.
  • Forces on an object have both a strength and a direction. An object at rest typically has multiple forces acting on it, but they add to give zero net force on the object. Forces that do not sum to zero can cause changes in the object’s speed or direction of motion.
  • Cause and effect relationships are routinely identified, tested, and used to explain change.

I quickly recognized that my first crack at this lesson was a bit too ambitious. Asking students to simply explore “balanced” forces proved difficult as we hadn’t gone over the difference between balanced and unbalanced. In hindsight, changing the lesson to simply explore how forces affect an object’s motion in any setting would have been preferred and students could likely come to some explanation of balanced versus unbalanced during classroom discussions. Also, my sentences starters (or lack there of) in the observations section left students expressing difficulty with turning all of their great observations and oral explanations into written expression. I will definitely be improving the data table so that all students must first explore a few basic force systems before exploring on their own. This will give all students common experiences to discuss in their class science circle before exploring on their own with some more complex arrangements.

Aside from the challenges, this experience affirmed by belief that the model would be a great fit for our classroom. The students manipulated the force systems easily and were firmly engaged. The video demonstrates students sharing some fairly sophisticated assessments of what’s going on in their simulation, albeit with some less than sophisticated terminology. A science circle or “Socrative Circle” provided a great time to introduce some of these terms to students as they shared their explanations of what was happened in different forces scenarios. The lesson also provided a great opportunity to squeeze in a very observable cause and effect relationship, one that is at the foundation of forces and motion and one of the seven NGSS crosscutting concepts to boot.

About Sean Musselman

Teacher Dad and Burlington MA Schools K-5 Science and Social Studies Curriculum Coordinator. NSTA Professional Development facilitator and author of "Think Like a Scientist: Investigating Weather and Climate" NSTA Kids ebook.
This entry was posted in 3-5, Curriculum, NGSS, Professional Reflections and tagged , , , , , , , . Bookmark the permalink.

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