Force and motion


1. Identifying and Sorting Mechanisms


Each group is provided with a varied collection of manufactured mechanisms, such as can openers, scissors, nail clippers, and pliers. First, they make general observations about these devices. Then students look at common characteristics of these devices, and try to determine what properties they share. Finally, the groups sort their mechanisms according to their own secret categories, and challenge other groups to guess their categories.


For the class: Chart paper and markers

For each group

  • Mechanisms: For each group about 8 different mechanisms such as scissors, snack food clips, barbecue tongs, clothes pins, can openers, nut crackers, lemon squeezers, egg slicers, garlic presses,tweezers, eyelash curlers, nail clippers, staple removers, pliers, and glue sticks. About half of these are supplied; the others can be gathered from students, home, and your own classroom.
  • Post-its ™, several per group

For each student: Science notebooks


  1. Exploration of mechanisms: Divide students into groups of 4 or 5. Provide each group with a collection of manufactured mechanisms. Students make a list of what they notice. (See video on observations of mechanisms). Here are some prompts for students as they observe:

    • What moves?
    • What doesn’t move?
    • What paths do the parts follow?
    • What do you do to make it work?
    • What does it do, and where does it do it?

  2. Collecting observations: Each group reports one observation. Record different observations on chart paper, then go around the groups for further observations, until their lists are exhausted. Relate the words “input”, “output”, and “pivot” to the observations that students make. (See video on analyzing student observations.) From the list of observations identify observations that relate to how you operate the mechanism, what the mechanism does, and how the mechanism is made.
    a. Student observations of their mechanisms include:

    • what you do to use them: they work by hand, you have to push or pull, you need to move them to make them work, it takes force, etc.
    • what they are used for: each one has a job to do; they cut, squeeze, mash, poke, grab or break something, etc.
    • how they are made: they all have moving parts, there’s a pin or pivot, there’s a little circle holding it together, this part doesn’t move but the others do, etc.
      b. Important mechanism words are:
    • Input: the location where you have to do something, to operate the mechanism.
    • Output: the special thing the mechanism does. It is the outcome of supplying the input.
    • Pivot: a pin or joint that holds everything together, allowing the other parts to rotate

  3. Sorting game: Guess my rule! Each group sorts its mechanisms into categories (see how the game is played). Encourage students to go beyond the familiar categories of size and color (see video). After each group is set on its sorting, the class goes from group to group trying to guess the sorting rule that was used. As a class review the different ways groups found to sort their mechanisms.

  4. Science Notebooks: Students draw and explain their devices. Here are suggestions for student recording.

  5. Extensions: More advanced categories. The categories students use reflect different ways to organize things. Click here for science categories, math categories and engineering categories. Everyday mechanisms can also be categorized as to their class(es) as levers.


Much of students’ sorting experience has been with respect to physical properties such as size, color and material. “How to look at mechanisms” is a video on encouraging students to look deeper at how things work, what they are used for, how many parts they have, how the parts are arranged, or how they move. The video “Use different categories” encourages students to sort things in new ways.