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Rotational mass

  1. Jun 28, 2007 #1
    1. The problem statement, all variables and given/known data
    suppose a block with mass m is being pulled by force f,the force of friction (first static then kinetic) will resist its motion.
    now, take this block and put it on a cart with wheels and pull it with the same force,when calculating the acceleration of this loaded cart,is it just a matter of calculating rotational and translational motion of the wheels does the wheight of the block on the cart matter when it comes to how fast the cart will accelerate? or is it just the moment of inertia of the wheel itsel?:confused:


    2. Relevant equations



    3. The attempt at a solution
     
  2. jcsd
  3. Jun 28, 2007 #2
    I'm confident that you can reason the answer to this question yourself.

    As a guide, consider the following example:

    When you're in a grocery store and you first get the shopping cart from up front, it's fairly easy to whip that thing in and out of aisles. Very soon; however, the cart begins to become more sluggish. Eventually, after piling in countless boxes of cereal, a gallon of milk, some steak, a lobster tail, chocolate chip cookies, nutri-grain bars, icecream, and that loaf of bread, you'll be doing good to make the turn down aisle 11 without knocking over the self-checkout registers. And if some tasty-looking treat catches your eye and you stop moving, may God be with you in getting that damn thing moving again. :wink:


     
    Last edited: Jun 28, 2007
  4. Jun 28, 2007 #3

    Chronos

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    It sounds like friction is being ignored [as well as the mass of the cart]. In that case, you can do a straightforward F=ma calculation where acceleration is the only quantity not given.
     
  5. Jun 28, 2007 #4
    thanks guys...it makes sense, but here is my problem:in all the physics problems i saw, dealing with rotational and translational motion, only the acceleration of one wheel being pulled by a force was discussed; are there any physics problem that deal with the acceleration of a load carried by two wheels?(a wagon,cart what have you) how would the calculation differ? thx very much for your help
     
  6. Jun 29, 2007 #5

    Chronos

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    The mass of the load does matter. The wheel size, or number of wheels, does not matter [even if they are of different sizes]. All wheel surfaces accelerate at the same rate. RPM's are the only theoretical variable. In the real world [i.e., the world of engineering] the problem is more complex - mainly because friction cannot be ignored.
     
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