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B Stop rubber from bouncing

  1. Jul 31, 2018 #1
    Is there anyway to stop rubber from bouncing? My class is doing an experiment on material absorption. I have been given the task to stop a rubber ball from bouncing. I was given a rubber ball that weighs 5 and a half ounces and has a circumference of 8 in. My material can't be over an inch thick. I have tried different types of foam and PVCs, no such luck. The challenge is we have to mount the material to the wall and then throw the ball as hard as we can at the material. Suggestions? Keep in mind I'm in school and don't have lots of money to spend
     
    Last edited: Jul 31, 2018
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  3. Jul 31, 2018 #2

    mfb

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    Too soft and the ball just compresses it before bouncing off the compressed material, too hard and the ball will bounce off the original surface. There should be some ideal compressibility in between.

    A liquid is not possible, I guess?
     
  4. Jul 31, 2018 #3
    No liquid. Perhaps a gel of some sort? But what to put the gel into that could withstand such an ampact?
     
  5. Jul 31, 2018 #4

    jbriggs444

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    Fly paper attached to rubber bands?
     
  6. Jul 31, 2018 #5
    Some ideas:
    1) A soft elastomer that has a high damping factor, such as Sorbothane: https://www.sorbothane.com/material-properties.aspx
    2) Something that absorbs energy without bouncing the ball back, such as a big water balloon.
    3) Another way to absorb energy is hang a large piece of heavy fabric, such as a tarp or canvas, a couple inches in front of the wall.
    4) You could also try hanging a piece of cardboard a couple inches in front of the wall.
    5) Some sort of air bag. It will need a properly sized vent hole - too small and the ball will bounce, too large and the ball will hit the wall. You should be able to make something from a garbage bag and duct tape. Or packaging tape.
    6) A bag of Jello?
    7) A plastic solid applied to the wall in a thick layer. Peanut butter? Roofing tar? The layer would need to be over an inch thick.
    8) Put the plastic solid in a bag. Less mess, and peanut butter would still be good to eat afterward.

    It's a great project. Have fun.
     
  7. Aug 1, 2018 #6

    sophiecentaur

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    How about a few layers of hessian or muslin, supporting an appropriate wet mix of wallpaper paste?
    A composite of some sort will perform better than a homgenous substance.
     
  8. Aug 1, 2018 #7

    jbriggs444

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    Does the ball have to be re-usable after the impact? A bed of barbed nails could be fun.
     
  9. Aug 1, 2018 #8

    sophiecentaur

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    How does that idea go with the dreaded 'sustainability'? :wink:
     
  10. Aug 1, 2018 #9

    phinds

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    Good suggestions in general but they don't meet the requirement stated so not good for this problem.
     
  11. Aug 1, 2018 #10
    Does it have to be fully stopped, or is it acceptable just to substantially reduce the rebound? Are. you allowed to cover both the ball and the wall with velcro?
     
  12. Aug 1, 2018 #11

    sophiecentaur

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    That requirement is very tough because the ball it big compared with the permitted thickness of the layer. The material of the layer has to be adhesive because there will be significant potential energy stored by the distortion of the ball during the impact. How ever much energy is absorbed by a 'high loss' material, the ball will still bounce off the wall unless it is actually stuck.
     
  13. Aug 1, 2018 #12

    phinds

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    I certainly do agree w/ that.
     
  14. Aug 1, 2018 #13

    sophiecentaur

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    I guess the challenge is a good one because no one is likely to stop the bounce completely; there will be a whole range of results.

    How about molten tar on the wall?
     
  15. Aug 1, 2018 #14

    fresh_42

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    Professional Mini Golfers have several dozens of different balls ranging through all varieties of possibilities of friction, elasticity etc.
     
  16. Aug 1, 2018 #15

    phinds

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    I think the best bet under the circumstances would be a heavy wool blanket hung 1" from the wall and extending several feet both up and down from where the ball is to hit. Even with having only 1" in which to move back at the point of impact, the weight of the blanket as it deforms to the point of impact would slow the ball considerably
     
  17. Aug 1, 2018 #16

    fresh_42

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    I have seen balls made of rubber which stuck on the ground the moment they hit it.
     
  18. Aug 1, 2018 #17

    phinds

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    Yeah, but that would be a particular KIND of ball, not likely the one he has to deal with. If it WERE the kind he has to deal with there wouldn't even be any problem so I don't see how that's helpful to this thread. Putting some heavy lead shot inside the ball would likely work too since that would make it act like a dead-blow hammer, but again, not the kind of ball this problem is about.
     
  19. Aug 1, 2018 #18

    Vanadium 50

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    How about a depolymerizing agent on the wall instead? :wideeyed:
     
  20. Aug 1, 2018 #19
    Whatever you put on the wall needs to absorb the kinetic energy of the ball, then not push the ball back.

    Some more ideas:
    1) Crush something. Try Styrofoam or several layers of cardboard. Crushing is a good way to absorb kinetic energy in a small distance.
    2) Most foam rubber is too soft by itself. It will compress, then the ball will bounce off the wall. You could saturate the foam rubber with a liquid. Start with water. If that's too thin, then a liquid that is more viscous. Corn syrup is a cheap viscous liquid, and you can adjust the viscosity by diluting with water. And cleanup is easy.

    Test as many different things as you can. The more things you test, the more you will learn. And have fun.
     
  21. Aug 1, 2018 #20

    Tom.G

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    Sand in a bag. And as @jbriggs444 said, maybe cover it with fly paper.
    Modeling clay. Again, maybe cover it with fly paper.
    Possibly a plastic bag filled with wet cornstarch. Change the water content to adjust the way it behaves. Once more perhaps with flypaper.
    Wet clay (as from the ground) in a plastic bag. It may or may not be easily available where you are.
    Several layers of bubble wrap packing material
    Wood shavings as used for packing material. (Known as excelsior.)
    The blanket with fly paper could be the best approach yet.

    A mix of any or all of the suggestions.

    Please let us know what you find and how the experiment works out!

    Cheers,
    Tom
     
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