Force & Motion - The Basics Net Force

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SWBAT describe force as an interaction of pushes and pulls between objects.

Big Idea

What forces are at work when objects move?

The Need for the Lesson

A force is an interaction between objects. Many middle school students harbor the misconception that force is a property of objects. For example, students may believe that when you throw a baseball, the force is transferred to the ball. 

When you see a game of tug-of-war, you cannot see the strength and direction of the participants. Using the PhET Simulation - Forces and Motion: Basics -- students will be able to see the strength and direction of forces being applied to objects and be able to make predictions about the motion of the objects.

Investigation Summary & Preparation

5 minutes

In this lesson students will observe how applied forces can change an objects motion.(MS-PS2-2 Plan an investigation to provide evidence that the change in an object’s motion depends on the sum of the forces on the object and the mass of the object.)

Disciplinary Core Ideas of Forces and Motion:

PS2.A The motion of an object is determined by the sum of the forces acting on it; if the total force on the object is not zero, its motion will change. The greater the mass of the object, the greater the force needed to achieve the same change in motion. For any given object, a larger force causes a larger change in motion. And all positions of objects and the directions of forces and motions must be described in an arbitrarily chosen reference frame and arbitrarily chosen units of size. In order to share information with other people, these choices must also be shared.)

The Cross Cutting Concept is Stability and Change.

The simulation include options to view visual displays that will help students strengthen their claims supporting the CCSS ELA standard integrating visuals to clarify understanding and provide evidence to support student claims. (SL.8.5 Integrate multimedia and visual displays into presentations to clarify information, strengthen claims and evidence, and add interest.)

Student engagement is supported as students use the Forces and Motion: The Basics simulation as a model to explain the concepts of force and motion. Students are also developing perseverance as they extract evidence through inquiry to support their understanding of force and motion. By changing variables to deepen their understanding, students are developing mastery as they use the simulation as an iterative process. (SP2 - Using Models)

Conducting investigations is inherent in all the PhET simulations as they allow for the change of variables that allow students to make changes in their investigation that lead to the discovery of answers to specific questions. Students in this simulation are changing variables in the simulation to understand the relationship between force and motion of objects. (SP3 - Planning and Conducting Investigations)

Throughout their investigations students are asked to collect observations and use the information collected to make conclusions building upon their experiences to develop habits and skills leading towards independent explorations. The lesson asks students to collection observations in a table and use that information to state conclusions about their investigation. (SP8 - Collecting and Communicating Information)

A complete materials list can be found in the resource section.

This lesson was inspired by:

PHET INTERACTIVE SIMULATIONS. "Simulate Net Forces to Predict an Object’s Motion." Science Friday. Science Friday Initiative, 10 Dec. 2014. Web. 2 May 2015.

Students in Action

40 minutes

Students in Action

I give students a few minutes to answer questions 1 & 2 with their elbow partner. The strategy is Turn/Talk/Record. Students are discussing the questions together and being help accountable for their discussion by recording their answers. Before going to the website, I ask students to share out their answers to questions 1 & 2. This is a mini formative assessment to see if students need more support to build adequate background knowledge before continuing to independently explore the simulation. Middle school students bring a wide range of background knowledge from elementary school so this step is a helpful probe to check for understanding.

PhET Simultation Force & Motion: The Basics Link

We use the HTML5 version of the simulation. This format works on both PCs and IOS devices. It also does not require a download so we do not have to work about problems downloading a Java version.

In this video, I explain the focus of the lesson and what I demonstrate for the students to get them started with the simulation.

As students work through the lesson, I circulate through the classroom to be sure the settings are correct and they are collecting the appropriate observations and using evidence from these observations to support their conclusions. 

I stop by each group to listen in as they discuss the answers to the followup question #5. My goal is for students to have observed the patterns they need to make predictions about how the force applied will change the motion of the object.

Connecting the Learning

10 minutes

Can you create balanced forces on this lever using only a nickel and a penny?

I give students a ruler and a fulcrum to create a first class lever. I share with them that we used to have playground equipment called teetor-totters. Some of my students are lucky enough to have their own experience with teetor-totters. I explain that I often took my young brother to the playground. He is 12 years younger and at the time, much smaller than myself, yet we were able to play on the teetor-totter. How did we do it?

Students should be able to determine where the heavier person (represented by the nickel) would sit and where the lighter person (represented by the penny) would sit in order to enjoy the teetor-totter. 

This hands-on culminating activity prepares students to tackle the next PhET simulation - Balancing Act where students apply math skills to balance objects.