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How to determine minimum required force in an applied context

  1. Mar 16, 2013 #1

    I am a graduate student in psychology and I've encountered an issue in one of my studies that is outside of my expertise, but hopefully within one of yours.

    Here's my predicament:

    I recently conducted a study with infant participants that investigated infants' ability to solve a simple problem involving two blocks of differing mass (one 70 grams and the other 470 g.) and a piece of cloth. The problem that infants must solve is this: one block is placed on top of the cloth, such that the block itself is out of their reach, yet the cloth is within reach, so infants must pull the cloth in order to retrieve the supported block. To publish my findings, I am being asked to report:

    1) for the 470 g block, what is the amount of force required to break static friction between the cloth and the table beneath it (which would cause the supported block to begin to move)?

    2) for the 70 g block, what is the amount of force required to break static friction between the cloth and the block, such that the cloth would move separately, leaving the block behind?

    In solving #1 and #2, all factors are identical (e.g., direction of force, acceleration, materials of the item, etc.) except for the mass of the block and the point of breaking static friction. I created a force diagram to better illustrate my problem---please overlook/forgive my lay explanation and terminology (i.e., I didn't include normal force or gravity in the diagram). Importantly, I am more concerned with the relative relation between the force required in these two situations, rather than the absolute value.

    What I'm wondering is, what is the best way to answer this problem? Is it possible to solve the problem in the abstract, that is, filling in approximationis for the relevant variables? Any suggestions you have are appreciated. Thanks

    Attached Files:

  2. jcsd
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