This isn't strictly a 'levers' experiment, but it's still a cool demonstration about simple machines, specifically how pulleys are connected with belts.

Take a rubber band and a roller skate (not in-line skates, but the old-fashioned kind with a wheel at each corner.) Lock the wheels on one side together by wrapping the rubber band around one wheel then the other.  Turn one wheel and watch the other spin.

Now crisscross the rubber band belt by removing one side of the rubber band from a wheel, giving it a half twist, and replacing it back on the wheel.  Now when you turn one wheel, the other should spin the opposite direction. Here's a quick video on what to expect:

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Comments

13 Responses to “Roller Skate Belts”

  1. arrowmakercpi says:

    i tried it with a toy car.it worked even when i stretched the rubber band around the rear view mirror that sticks out.(i used a plastic car not a hotwheels car)

  2. Ingrid Cordano says:

    🙂

  3. Ingrid Cordano says:

    I love it!:)

  4. Thanks for your eagle eye! It looks like you are right! I will correct this document and re-upload it for you.

    Let’s look at this together:

    velocity = v
    angular velocity = w
    radius = r

    v = rw

    The velocity at the point of contact is the same on both gears, so:
    v = rawa = rbwb

    so the equation is:

  5. Susan Plott says:

    Sorry about the abruptness in the wording on the previous comment. It was one of the children who sent it without me knowing it. It does appear that there is a typing error on the worksheet for advanced students in the formula for gear ratio. I believe it should be R = rb/ra = wa/wb. This is a great way for the students to picture angular velocity. Thank you for supercharged science! 🙂

  6. Susan Plott says:

    you made a mistake, R = Wa/Wb = rb/ra, not R = ra/rb = Wa/Wb .

  7. I would try a friend’s house! 🙂

  8. Becky Ulrick says:

    Can’t do the experiment because we don’t roller skates or skate boards.

  9. Jill Iovino says:

    We used a small skate board. Worked well. Thanks.

  10. Rachel Schaus says:

    🙂

  12. Vicki Jordan says:

    Same thing, we have roller blades,not skates.

  13. Carolyn Norville says:

    That is so cool except I do not have roller skates any more I think!