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published by the University of Colorado
This PhET simulation, now available in HTML5, lets students explore lever arm, torque, and static equilibrium through the context of a playground teeter-totter. It's a highly visual way to investigate how changing the position of a mass on one or both sides of the pivot point will affect the movement of the plank. Students will discover that there are mathematical relationships among mass, distance from fulcrum, and torque, which can be used to predict whether the system will balance or not.

This resource is part of PhET (Physics Education Technology Project), a large collection of free interactive simulations for science education.
Editor's Note: Activity can be easily adapted for middle school or high school. Lesson plans and student guides designed for varying ability levels are available on the PhET website. You must be a registered user to access the teacher-created lesson materials, but registration is free and easy.
Subjects Levels Resource Types
Classical Mechanics
- Statics of Rigid Bodies
= Equilibrium
- Middle School
- Informal Education
- High School
- Instructional Material
= Interactive Simulation
Appropriate Courses Categories Ratings
- Physical Science
- Physics First
- Conceptual Physics
- Activity
- New teachers
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Intended Users:
General Public
Access Rights:
Free access
This material is released under a Creative Commons Attribution 3.0 license. All use requires attribution.
Rights Holder:
University of Colorado, 2018
Torque, lever arm, torque
Record Creator:
Metadata instance created April 24, 2012 by Ed Lee
Record Updated:
September 1, 2018 by Caroline Hall
Last Update
when Cataloged:
May 26, 2015
Other Collections:

Next Generation Science Standards

Disciplinary Core Ideas (K-12)

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. (6-8)

Crosscutting Concepts (K-12)

Cause and Effect (K-12)
  • Cause and effect relationships may be used to predict phenomena in natural or designed systems. (6-8)
  • Systems can be designed to cause a desired effect. (9-12)
Scale, Proportion, and Quantity (3-12)
  • Proportional relationships (e.g. speed as the ratio of distance traveled to time taken) among different types of quantities provide information about the magnitude of properties and processes. (6-8)
  • Algebraic thinking is used to examine scientific data and predict the effect of a change in one variable on another (e.g., linear growth vs. exponential growth). (9-12)

NGSS Science and Engineering Practices (K-12)

Developing and Using Models (K-12)
  • Modeling in 9–12 builds on K–8 and progresses to using, synthesizing, and developing models to predict and show relationships among variables between systems and their components in the natural and designed worlds. (9-12)
    • Use a model based on evidence to illustrate the relationships between systems or between components of a system. (9-12)
ComPADRE is beta testing Citation Styles!

Record Link
AIP Format
(University of Colorado, Boulder, 2011), WWW Document, (https://phet.colorado.edu/en/simulation/balancing-act).
PhET Simulation: Balancing Act, (University of Colorado, Boulder, 2011), <https://phet.colorado.edu/en/simulation/balancing-act>.
APA Format
PhET Simulation: Balancing Act. (2015, May 26). Retrieved January 23, 2019, from University of Colorado: https://phet.colorado.edu/en/simulation/balancing-act
Chicago Format
University of Colorado. PhET Simulation: Balancing Act. Boulder: University of Colorado, May 26, 2015. https://phet.colorado.edu/en/simulation/balancing-act (accessed 23 January 2019).
MLA Format
PhET Simulation: Balancing Act. Boulder: University of Colorado, 2011. 26 May 2015. 23 Jan. 2019 <https://phet.colorado.edu/en/simulation/balancing-act>.
BibTeX Export Format
@misc{ Title = {PhET Simulation: Balancing Act}, Publisher = {University of Colorado}, Volume = {2019}, Number = {23 January 2019}, Month = {May 26, 2015}, Year = {2011} }
Refer Export Format

%T PhET Simulation: Balancing Act
%D May 26, 2015
%I University of Colorado
%C Boulder
%U https://phet.colorado.edu/en/simulation/balancing-act
%O text/html

EndNote Export Format

%0 Electronic Source
%D May 26, 2015
%T PhET Simulation: Balancing Act
%I University of Colorado
%V 2019
%N 23 January 2019
%8 May 26, 2015
%9 text/html
%U https://phet.colorado.edu/en/simulation/balancing-act

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Citation Source Information

The AIP Style presented is based on information from the AIP Style Manual.

The APA Style presented is based on information from APA Style.org: Electronic References.

The Chicago Style presented is based on information from Examples of Chicago-Style Documentation.

The MLA Style presented is based on information from the MLA FAQ.

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