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A New Spin On Motion

These activities will inspire your students to ask questions and seek answers about motion. Things that roll and spin behave in ways that are often surprising or counterintuitive.

Feel free to do these activities separately or together and please adapt them to the needs and abilities of your class.

Are you ready to get rolling (or rather, spinning) ?

When playing with different tops, you may notice that some spin longer than others. Heavy tops spin for a longer time than light ones when launched at the same speed. The faster they’re spinning when launched, the longer they spin. The combination of mass and speed is known as momentum.

Mathematically, momentum is mass times speed.

MOMENTUM = MASS x SPEED

So, a 1kg rabbit going 40km/h has the same momentum as a big 40kg dog ambling along at 1km/h. The more momentum something has, the harder it is to stop. But what stops the top? Friction between the stick and the floor is the main culprit.

The momentum of spinning and rolling things is called angular momentum.

With tops, is that it matters where you put the weight. The farther away from the stick the mass is, the more angular momentum the top has and the harder it is to stop.

ANGULAR MOMENTUM = MASS x SPEED x DISTANCE BETWEEN THE MASS AND THE AXIS OF ROTATION

What about getting things moving in the first place?

To make something move, you need a push or a pull force. To make something roll or spin, the force has to be some distance from the object’s centre of mass. When you launch your tops using an elastic band, you pull from the side of the stick, just beside the centre of mass. The energy stored in the stretch of the elastic band is transferred to the top.

The heavier something is, the more force you need to make it move. When something is hard to move, it has lots of inertia. When something is hard to spin, it has lots of rotational inertia. Rotational inertia depends on the mass of an object and where the mass is located. The farther the mass is from the axis of rotation, the harder it is to make the object spin or roll.

Objectives

  • Build tops and use various methods to make them spin.

  • Investigate the concepts of inertia, momentum, force and centre of mass, as they apply to tops.

  • Carry out a scientific experiment by: making careful observations; formulating testable questions; performing multiple trials; and by changing one variable at a time.

Materials

  • Part 1

    Commercial tops and top-like items (rattlebacks, tippy tops, gyroscopes)

    For each top (Per Student or Per Group):
    1/4 inch dowel, 25cm long
    10-inch Styrofoam® or stiff paper plate
    2 x #8 single-hole rubber stoppers (can be ordered from scientific supply companies)
    large nail or sharp pencil to punch holes
    liquid soap (helps the dowel slide through the stoppers)
    felt markers and other art supplies for decorating tops
    launcher

    rubber band launchers can be made of made of:
    strip of wood approximately 5cm x 2cm x 40cm (we used pieces of wood known as a one by two)
    2 long, wide elastic bands (#64 or equivalent) tied
    together
    3 cup hooks

    String launchers can be made of:
    string about 75cm long
    large bead or empty thread spool

    Part 2

    Basic top supplies from Part 1
    extra paper plates and #8 rubber stoppers
    pencil
    masking tape
    stopwatch or clock with a second hand

    Items to add weight to tops, such as:
    nuts and bolts
    washers
    paperclips
    bulldog clips
    plasticine

Key Questions

  • How and why do tops spin in different ways?
  • How can we use observations to help us learn more?

What To Do

Part 1: Make Your Own Top

  1. Brainstorm. Solicit students’ ideas about tops. Prompt them with questions like:
  • Does anyone own one?
  • What does it look like?
  • Have you ever played with one?
  • What can you tell me about the way they work and behave?
  • Where can one find tops in our everyday world?
  • Has anyone ever spun around or been a top?
  • Has anyone ever ridden a top? What was that like?
  • Did you notice or do you remember anything special about tops?

Teacher Tip: Depending on how much experience your group has had with tops and spinning toys, you may want to start with time for the students to play with a variety of commercial tops.

  1. Build the top.
    1. Find the centre of your paper plate by balancing it on your finger. If the plate balances, your finger is at the centre of mass. Use the nail to poke a hole through the plate at that point.
    2. Dip one end of a 25cm-long dowel in liquid soap, which will allow the dowel to slide through the stoppers more easily.
    3. Put one stopper on the dowel and slide it along about a quarter of the length.
    4. Put the dowel through the hole in the plate, with the plate’s top side facing the stopper.
    5. Slide the other stopper on from the bottom, so that the stoppers sandwich the plate, and push the stopper tight up against the plate. There should be about 2–3cm of dowel showing under the plate.
  1. Launch the top. Be sure to tighten the rubber stoppers after each launch (they will work themselves loose).

Rubber band launcher:

  • Attach two rubber bands together in a chain. Wrap one end of the rubber bands around the stick of the top a couple times. Put the stick in the two cup hooks of the launcher with the wrapping between the hooks.
  • Stretch the other end of the rubber bands to hook onto the single hook of the launcher. Wind the rubber band up by turning the stick around. Hold the stick firmly.

  • Let go of the stick with the top close to the ground. Once the top is spinning, lift the launcher free.

String and spool launcher:

  • Wrap the string around the stick of the top until there is about 5cm left over.
  • Put the top on the ground. Thread the end of the string through the spool.
  • Hold onto the spool, but don’t hold the stick. Pull the string—slowly at first, then faster.

Hint: Tops spin well on uncarpeted floors. If you have a carpet which interferes with your tops, spin them on the lids from ice cream pails.

  1. Compare Results. Have the students share their successful launch methods with each other. Make sure they have lots of time to practice different launch methods before trying to modify their tops.

Teacher Tip: CROSS-CURRICULAR CONNECTIONS

Tops figure into many cultural traditions. Investigate, for example, dreidels, giant wooden tops used since the tenth century in Ta Hsi in Taiwan, or those tops used by the Haida and Tsimshian of the Pacific West Coast.

Part 2: Top Investigations

  1. Observe your top in action.
  • Using the tops you built in Part I, launch them and observe what they do. Use all your senses! Describe their motion as carefully as you can. Compare them to commercial tops.
  1. Ask lots of questions.
  • Have students brainstorm questions that could be answered by experimenting with the tops. If the group is having trouble getting started, you could offer some suggestions. Here are some of the questions that arose when we started to play with tops:
    • Do tops that spin clockwise spin as long as tops that spin counter-clockwise?
    • Do heavier tops spin longer than lighter ones?
    • Does where you place weights on a top affect how long it spins?
    • Do tops that are made with paper plates spin longer if the plates face up or down?
    • Does a top made with a single plate spin longer than a top made with a stack of plates?
    • Do tops with the flywheel near the top of the stick spin longer than those with the flywheel near the bottom?
    • Do tops spin better on some surfaces than on others?

Hint: Try using yogurt containers, rubber balls, CDs or pizza pans as alternative flywheels.

  1. Design an experiment.
  • Ask the students to offer suggestions on ways that they might find the answers to their questions. For example, you can add weight to your top by sticking bolts through the paper plate, by putting washers over the stick, or by adding more plates or more stoppers. You can arrange the plates in different ways along the stick. You can draw on the flywheel to see what the spinning design looks like.

Teacher Tip: WHEN YOU’RE DOING A SCIENTIFIC INVESTIGATION

  • Do each experiment several times to avoid drawing conclusions from something that happened by chance.
  • Change only one variable at a time. A variable is an ingredient in the experiment that you can change to see if the top spins differently. For example, you might add weights to the top. If you change many variables at once and the top behaves differently, it will be very difficult to determine which variable(s) made the difference.

For example, if you add weights and also try a new method of launching your top, you will not know which caused the change in top behaviour.

  • Be clear about what is meant by better (are you measuring spin time, observing stability?).
  • Record your results.
  1. Experiment!
  • You may want to have the whole class work on a single experiment together or you might allow each pair of experimenters to choose their own question to explore. Give them plenty of time to carry out their experiment. The students should keep a record of their investigations.

Teacher Tip: This might be a good time to introduce your students to using charts and tables to keep track of results.

  1. Discuss the experiments.
  • Have students share the methodology and results of their experiments. Introduce the words force, inertia, momentum and centre of mass as appropriate, to help the discussion along. Record observations on a blackboard or chart paper.
  1. More experiments!
  • Allow more time for experimentation – students may want to try other groups’ ideas or pursue their own further.
  1. Closure.
  • Review key concepts. These can include observations about the motion of the tops and comments on the process of scientific experimentation.

Teacher Tip: CROSS-CURRICULAR CONNECTIONS

A top made with a felt marker or a pencil as a stick creates surprising and beautiful artwork. Wool can be spun with a hand spindle, which uses a spindle whorl as a flywheel to add momentum to a spinning stick. Coast Salish artisans have traditionally decorated their spindle whorls in a way that creates fascinating patterns as the whorls are spun. Contemporary artist Susan A. Point creates decorative spindle whorls in this tradition.

Extensions

  • Allow more time for experimentation. Students may want to try other groups’ ideas or pursue their own further.
  • Spinning things have remarkable stability. Investigate how gyroscopes are used to keep satellites stable.Experiment with throwing a football or a Frisbee®, both with and without spinning it. How does the spin affect the way it flies?

Other Resources

Science World Resources | Toupies mouvementées | French version of this resource