Half a croissant, on a plate, with a sign in front of it saying '50c'
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Endless freefall

Not really, but it's still cool looking.
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You will need an adjustable speed treadmill and a basketball. Elevate the aft end of the treadmill. The height (angle) will need to be adjustable. Turn on the treadmill, and place the basketball on the middle of the rotating mat. Adjust the angle and speed of the treadmill until the basketball remains in place. Voila! A cool looking display of a basketball rolling down an incline but never gets to the bottom.
hessenfeff, Aug 21 2008

Okay - Here we go again http://www.youtube....watch?v=pv5zWaTEVkI
[normzone, Aug 21 2008]

[link]






       Oops. I think I just voted for my own invention. Please bear with me, first post. Greetings to all.
hessenfeff, Aug 22 2008
  

       pssst, I think it's allowed.   

       Now I know what to use as my centerpiece for the bar mitzvah.   

       [l'chaim!]
WhereYouAt, Aug 22 2008
  

       Suppose we put some different size/mass balls on the treadmill. Couldn't we have some balls slowly rising, some slowly descending, and some rolling in place at the same time?
hessenfeff, Aug 26 2008
  

       Does not work unless there is considerable friction arresting the acceleration of the ball such as it having some sand in it or a very rough surface to cause air resistance. To help you understand why imagine placing a ball bearing on a pencil then touching the bearing to the face of an inverted belt sander. A bearing in good condition will immediately accelerate to the speed of the belt with very little pressure against the pencil. The tendency of the pencil to move forward could be described as the "drag" of the bearing. Once the system is in equilibrium the drag is very uniform and the angle of the sander could be set to compensate for the drag balancing the system against gravity. Then the only effect of drag that we would see is the torsional force of the drag on the pencil itself which we are resisting with our fingers. The system is now "balanced". But if we took our fingers off the pencil the drag exerted by the bearing on the pencil would be reduced as the pencil itself began to rotate pulled by the drag. As the frictional loss to drag is eliminated the top speed of the bearing (now solid) would increase exponentially and it would slowly fall off the bottom of the belt no matter how high you turned the speed. There must be a calibrated uniform drag designed into the system to limit the speed of the rotating member so that energy is removed equal to compensate for the gravitational acceleration of the rotating mass. Air resistance will not provide this drag unless the angle, and thus the speed are very low. Much more complicated than it seems and it would make great material for a college level engineering contest (who could make the fastest, or most stable perpetual system. )
WcW, Aug 26 2008
  

       Welcome. Here's a bun.
Voice, Aug 27 2008
  

       can we do this with meatballs in marinara making a stationary meatfall?
Arcanus, Apr 23 2010
  

       If one uses expandable cylinders or spheres rotational energy can be used to expand them rather than speeding up the rotation. If they're quite heavy on the outside they could absorb quite a bit of energy as momentum. Alternatively one could increase air friction.
Voice, Mar 14 2011
  

       //Alternatively one could increase air friction.// Now there's something. If only you had benouilli-er with that post.
4whom, Mar 14 2011
  

       If anybody remembers Tribbles, I could see a bunch of those things "jogging" on a propery adjusted treadmill.
doctorremulac3, Mar 15 2011
  

       A soft belt (carpet or similar) would work to increase the rolling friction of the ball, helping to balance it.
MechE, Mar 15 2011
  
      
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