Note: Do the pendulum experiment first, and when you’re done with the heavy nut from that activity, just use it in this experiment.


You can easily create one of these mystery toys out of an old baking powder can, a heavy rock, two paper clips, and a rubber band (at least 3″ x 1/4″).  It will keep small kids and cats busy for hours.


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Here’s what you get:


  • can with a lid
  • heavy rock or large nut
  • two paper clips
  • rubber band

You’ll need two holds punched through your container  – one in the lid and the bottom. Thread your rubber band through the heavy washer and tie it off (this is important!).  Poke the ends of the rubber band through one of the holes and catch it on the other side with a paper clip.  (Just push a paper clip partway through so the rubber band doesn’t slip back through the hole.)  Do this for both sides, and make sure that your rubber band is a pulled mildly-tight inside the can.  You want the hexnut to dangle in the center of the can without touching the sides of the container.


Download Student Worksheet & Exercises


Now for the fun part… gently roll the can on a smooth floor away from you.  The can should roll, slow down, stop, and return to  you!  If it doesn’t, check the rubber band tightness inside the can.


The hexnut is a weight that twists up the rubber band as the can rolls around it.  The kinetic energy (the rolling motion of the can) transforms into potential (elastic) energy stored in the rubber band the free side twists around. The can stops (this is the point of highest potential energy) and returns to you (potential energy is being transformed into kinetic). The farther the toy is rolled the more elastic potential energy it stores.


Exercises


  1. Explain in your own words two types of energy transfer:
  2. True or false: All energy in a system is lost to heat.
    1. True
    2. False

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Comments

8 Responses to “Mystery Toy”

  1. I am sorry for the access issues – we’re still trying to fix them, it’s totally our fault. I am rechecking the site now, let me know if still doesn’t give you access?

  2. elainehrrsn says:

    This experiment was on the DVD we received by mail. I watched it last night but am away from the DVD right now. I wanted to have Michelle watch it now, but it says no access.

  3. Oh no! Feel free to send me images/video to aurora@superchargedscience.com – take an image of the inside your can and also how it rolls. What happens if you try different weights and different tensions on the rubber band?

  4. We couldn’t get it to work! We tried a couple different ways. It just rolled around wobbly.

  5. Yes, I am sure you can get it to work – give it a try!

  6. lorin_mcguire says:

    What if you use a toilet paper roll and a rock?

  7. Perhaps, or that it’s not winding itself up because they are too tight. Take a look at how it winds when you hold it in your hands and gently rotate it to simulate the rolling motion.

  8. valeska_holme says:

    Ours is not coming back to us if we give it more than a very gentle push. Is it because the rubber bands are too stretched out inside the can?