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I How to calculate force on stationary wall?

  1. Jul 12, 2016 #1
    What is the right method to calculate force the that is
    applied (by human) on the stationy wall?
     
  2. jcsd
  3. Jul 12, 2016 #2

    Doc Al

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    You'll need to be a bit more specific. What is the situation you are analyzing?
     
  4. Jul 12, 2016 #3
    Me (Mr.Raza) apply froce on the wall then how i calculate that applied force
     
  5. Jul 12, 2016 #4

    Doc Al

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    Unless there are more details, it doesn't sound like there is sufficient data to calculate the force. After all, I can push a wall with all my might (thanks to friction between my shoes and the floor) or I can just lightly touch the wall.

    You might be able to measure the force, given the right equipment.
     
  6. Jul 12, 2016 #5
    For example if my mass is 60kg and co-efficient of friction is .5 then please calculate the force
     
  7. Jul 12, 2016 #6

    Doc Al

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    Not enough information.
     
  8. Jul 12, 2016 #7
    Please sir give me an example such that i completly understand it.
     
  9. Jul 12, 2016 #8

    Doc Al

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    Let's take a side trip for a moment. It sounds like you want to learn how to solve a certain kind of problem. True? If so, give me an example of the exact problem you are trying to solve.
     
  10. Jul 12, 2016 #9

    Nidum

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    If you are standing up and pressing with one hand on the wall then force can be from nothing up to the limit of the force that you can apply .

    The limit on the force that you can apply is set by your strength and by your stability .

    Stability relates to how much force you can apply before you start pushing yourself away from the wall .
     
  11. Jul 12, 2016 #10
    Then, the reaction is N = mg; N = 600 N (g ≈ 10 m/s2). This is a vertical force.
    The friction is Ff = μN; Ff = 300 N. This force is horizontal.

    Jehangeer Raza, when you push the wall, is your force horizontal or vertical?
     
  12. Jul 13, 2016 #11
    Horizental force
     
  13. Jul 13, 2016 #12

    Doc Al

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    This assumes that the force against the wall has no vertical component.

    This would be the maximum friction force possible (given the assumption of a purely horizontal push against the wall).
     
  14. Jul 13, 2016 #13

    Nidum

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    Inclination of the body matters in this calculation . Distribution of forces is different depending on whether body is upright , leaning forward or leaning backwards .

    You will have seen people trying to move a stalled vehicle by pushing from behind . They intuitively lean forward at quite a steep angle so as to be able to generate maximum pushing force and obtain maximum footing reaction force before slipping .
     
  15. Jul 13, 2016 #14
    Jehangeer Raza, let's have a look at the following situation.
    Consider a box on a surface with friction. When you try pushing it with different forces, you obtain different results.
    Assume, the parameters are the same, m = 60 kg, μ = 0.5 - for the motionless box. I add another value: μm = 0.3 - for the moving box.
    Can you tell, what forces act on the box if your horizontal push is 100, 200, 300, 400 N?
     
  16. Jul 13, 2016 #15
    The question is interesting and useful. One practical application could be calculating the force exerted on the handrails of footbridges. Given the width of the footbridge and the height of the rail, one could calculate the probable force exerted on the rail by making certain assumptions as to angle of the body and, if desired, any momentum effects. On our footbridge construction I simple took a bathroom scale, held it at railing height and pushed against it. Adding a safety factor of three gave me a stress design factor. That was fifteen years ago and so far no one has tested the rail by falling against it.
     
  17. Jul 13, 2016 #16

    CWatters

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    Trust the military to know..
    http://www.dtic.mil/dtic/tr/fulltext/u2/720252.pdf

    "Horizontal Static Forces Exerted By Men Standing In Common Working Positions On Surfaces Of Various Tractions Including Coefficients Of Friction Between Various Floor And Shoe Materials"

    K. H. E. Kroemer, et al
    Aerospace Medical Research Laboratory
    Wright-Patterson Air Force Base, Ohio
    January 1971

    Abstract

    Experiments were conducted to measure maximal isometric horizontal push forces. Twenty-eight male subjects pushed forward with both hands, laterally with the preferred shoulder, and with their backs. Reaction force for body stabilization was provided by a vertical wall, a footrest, or by floor-shoe combinations with coefficients of static friction of approximately 1.0, 0.6, and 0.3. Means, standard deviations, and 5th percentiles of the exerted forces are reported. In comparing the experimental data with results previously published, it is concluded that body weight cannot serve as a reliable predictor for push forte capability from floors of various tractions. Estimates for static horizontal push as well as pull force capabilities of one or several men are tabulated in relation to traction available to the operator. An appendix contains coefficients of static friction between nineteen floor materials and eight shoe materials.
     
  18. Jul 13, 2016 #17
    Cool )

    I believe, this kind of experiments must be conducted by manufacturers of army/sports footear. To win tenders.
     
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