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-   -   Friday afternoon physics (https://www.askmehelpdesk.com/showthread.php?t=93873)

  • May 18, 2007, 11:49 AM
    ebaines
    Friday afternoon physics
    I have a typical cable reel, constructed of a central hub that the cable winds around and two end flanges of larger diameter. If I place the reel upright on its flanges on the floor, and unwind some of the cable in such a way that the cable comes off the underside of the hub towards me, and then pull on the cable, which way will the reel roll? That is, will it try to roll towards me (winding up the cable as I pull), or will it roll away from me (unwinding the cable)? Assume the friction between the floor and the flanges of the reel is sufficiently high to prevent the reel from just spinning in place.

    I have found that about half the people get it right and half wrong. What do you think?
  • May 18, 2007, 11:57 AM
    Capuchin
    I was trying to work out it coming from the overside, lol.

    Definitely and obviously it rolls away.
  • May 18, 2007, 12:00 PM
    J_9
    Sheesh, I hope I get this one right!!

    It rolls away
  • May 18, 2007, 12:29 PM
    ebaines
    Think it through again guys...
  • May 18, 2007, 12:58 PM
    Capuchin
    Heh of course, you get caught up into working out the direction of wheel spin and friction... itdoes roll towards you :)

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