Name of Activity



Kara Miranda


gear, gear ratios, build, machine, tug-o-war, competition, prototype, Engineering Design Process, torque



Grade Level

4, 5, 6, 7, 8, 9+


3 Hours Total

Brief Description

Students will use their knowledge about gears and gear ratios to build a machine that will play tug-o-war against another classmate’s.

Lesson Objectives:

To apply building techniques and knowledge about gears to an activity challenge.

Materials Needed:

RCX or NXT LEGO kits

Assortment of extra LEGO pieces, especially gears and beams

Engineer’s Planning Sheet




Preparation and Set Up:

Collect necessary materials Photocopy worksheets Arrange students into groups of 2 Decide how you will distribute extra pieces

Write design requirements on the board

Necessary Background

Review gears, gear ratios, and torque.

Vocabulary: Prototype Engineering Design Process


Gear ratio



  • Tell students that in this challenge they will be playing tug-o-war by building a machine that can provide enough torque to pull on another machine doing the same thing. String will be tied between the two, and a machine will have to pull the other over a line of tape in order to win.
  • Make sure to review how gears work, gear ratios, and using gears for torque vs. speed. Also explain the engineering design process.
  • Tell students the requirements for their tug-o-war contenders. Examples of requirements are:
  •       Must use gears
  •       Must have a sensor
  • Allow the class to brainstorm different ideas for their machines. Have them plan out and draw their design on the engineering planning sheet.
  • Distribute materials and have students start building. You may have to assist students with tying string to their machine.
  • After the students finish building, pair up machines and tie them to either end of a string, making sure the middle of the string is right above the tape on the ground, and that both machines are equidistant from the tape.
  • Have the students start their machines. Whoever’s machine gets pulled over the line first, loses.

  • After the students finish, review the activity with the class. Have them share their ideas, ask groups to explain what the hardest part of the challenge was, etc.
  • Extensions:

    Have students add more gears

    Make a classwide tug-o-war competition. Whose is the “strongest”?

    Allow those who lose to redesign and compete against each other again

    Reference 1


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