Rotational Equilibrium

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In this activity, learners explore the concept of rotational equilibrium. Learners work in teams to estimate and determine the force within a mobile design. Learners solve algebraic equations, apply graphing techniques, compare results and discuss findings. Designing the mobile requires learners to solve a set of two linear algebraic equations. Learners solve the equations using three different methods: by substitution, by graphing the equations and finding the intersection, and by using determinants.

Quick Guide

Preparation Time:
10 to 30 minutes

Learning Time:
1 to 2 hours

Estimated Materials Cost:
$5 - $10 per group of students

Age Range:
Ages 14 - 18

Resource Types:
Activity, Lesson/Lesson Plan


Materials List (per group of students)

  • Student Resource Sheets
  • Student Worksheets
  • 1/4 x 1/4 by 36-inch balsa wood stick
  • Pennies or similar object of uniform weight
  • Sewing thread or light string
  • Material on which to mount the pennies: e.g. construction paper, cardboard or poster board
  • Marking pen
  • Cellophane tape or glue
  • Scissors
  • Ruler marked in millimeters and centimeters or a meter stick


  • Engineering and Technology
    • Engineering
  • Mathematics
    • Algebra
      • Equations and Inequalities
      • Variables and Expressions
    • Data Analysis and Probability
      • Data Analysis
      • Data Collection
      • Data Representation
    • Geometry
    • Number and Operations
      • Fractions
      • Operations
  • The Nature of Technology
    • The Design Process
      • Problem Solving
  • Physical Sciences
    • Motion and Forces
      • Gravity
      • Momentum and Velocity
      • Rotation Motion

Informal Categories

  • Arts and Crafts
  • Toys


To use this activity, learners need to:

  • see
  • read
  • touch

Learning styles supported:

  • Involves teamwork and communication skills
  • Links STEM to other topics of interest such as arts and humanities
  • Involves hands-on or lab activities


Components that are part of this resource:

Includes alignment to state and/or national standards:

This resource is part of:

Access Rights:

  • Free access



  • All rights reserved, IEEE,