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Does this require More energy?

  1. Apr 7, 2006 #1
    Question scenario:

    Let's say that we have a heavy bowling ball and roll it across a horizontal platform that can be vertically raised.

    Experimental condition #1: The bowling ball is not moving, and I raise the platform with X amount of force directly underneath the static ball to raise the ball 1-foot.

    Experimental condition #2: the bowling ball is given a forceful horizontal movement along the surface of the horizontal platform and, at mid-point of travel, I raise the platform directly underneath the ball to raise the ball 1-foot.

    Does condition #2 require more upward force than #1 ???

    This is not a homework Q. Just curious. I assume the answer is yes.
     
  2. jcsd
  3. Apr 7, 2006 #2

    Doc Al

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    Staff: Mentor

    Why would you assume yes? Why would the amount of force required to raise the platform depend on the horizontal speed of the ball?
     
  4. Apr 7, 2006 #3
    I don't know, Doc, that's why I'm asking.

    Doc, my assumption, perhaps erroneous, is based on my notion that a horizontal momentum influences a vertical thrust.
    I find it rather odd that horizontal momentum does not negatively influence an outside vertical.
    Granted, the vectors are not opposing, but surely there would be a resultant vector shift. Perhaps this resultant vector shift does not oppose the applied vertical force, so, I have another question:

    Does your answer also apply with respect to a accelerating ball?
     
  5. Apr 7, 2006 #4

    Doc Al

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    I fail to see why a horizontal velocity (or acceleration) would have any bearing on the force required to produce a vertical acceleration.
     
  6. Apr 7, 2006 #5
    I find it hard to believe that a planar vector shift expends the same energy on a static-vs-moving mass. But I'm sure you are correct.

    Post edited.
     
    Last edited: Apr 7, 2006
  7. Apr 7, 2006 #6

    Doc Al

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    Not sure what you mean by "planar vector shift". The same vertical force exerted through the same vertical displacement will perform the same amount of work. (The horizontal displacement is irrelevant.)

    To just support the bowling ball a normal force is required. Does a horizontally moving ball require a greater normal force to support its weight? No.
     
  8. Apr 7, 2006 #7

    russ_watters

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    The question is ill-defined. You could apply more force case 2 if you wanted to - you haven't said how fast you are accelerating the bowling ball upwards in either case.

    The energy (from your title) is the same though: gmh.
     
  9. Apr 8, 2006 #8
    Very good. Thanks to both Doc and Russ for helping me to understand this better. I have always loved physics, and even know a thing or two, but sometimes the basics stump me!!
     
  10. May 1, 2006 #9
    perpendicular vectors are independent of eachother
     
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