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Force and motion

MechAnimations

7. Movement Around a Pivot

Overview

Students investigate movement around a pivot. What path is followed? How does the length of the path change with its distance from the pivot? If students are counting steps, what is a fair way to compare their distances? This lesson provides students an experiential basis to understand that as a lever moves around a pivot, points further from the pivot move more than points nearer the pivot.

Materials

  • 10’ rope with markers at 5’ and 10’, one for the class.
  • Pegboard bases and strips (one per student) and three rivets per student.
  • Paper to place on base for tracing input movement.
  • Ruler to measure length of tracings of the input movement
  • Science Notebooks

Procedure

  1. Introduce the concept of path: Demonstrate a pegboard base with the 0” hole of a lever connected to the bottom of the base. Place a marker at the end of the lever and move the lever from one side of the base to the other. Discuss the shape of the path that is followed by the marker. (See a video)

  2. Paths with a rope: While one end of a rope is held firmly, children at 5’ and 10’ from this pivot attempt to walk in a straight line. They explore their resulting movement. Here is a video on paths with a rope as well as ideas for procedures and questions.

  3. Paths of inputs on a pegboard: the set-up: Provide each student with a base, a numbered strip, three rivets, and pre-punched paper on which to trace input paths. Here are directions to set up the experiment and a video of the set up.

  4. Tracing input paths: Students put a pencil through the 2”, 4” and 8” holes of the lever, at each point drawing the path of the lever as it moves from the left-hand stop to the right-hand stop. A video illustrates drawing input paths.

  5. Whole-class meeting and discussion: Encourage students to discuss what is similar between the rope experiment and the tracings on the paper.

Outcomes

  • The paths followed by the students and the pencil on the lever are arcs,

  • The further the student or hole is from the fixed pivot, the longer the path.

    Science Notebooks: Here are prompts to which students may respond.