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Force on a ladder

  1. Oct 23, 2013 #1
    now imagine a ladder resting on the ground and the wall
    such that it makes a right angled triangle
    now if someone walks on the ladder , the part of the ladder resting on the wall is going to have a force pulling it down * the weight of the man *
    what is the force pushing the ladder horizontally ?
    if F1= F
    what is the magnitude of F2 ?
    is there even going to be an F2 ?
    if this is not a smooth surface
    can i just describe F2 as friction ? and it would be in the opposite direction

    F1 is the force due to the ladder pushing on the wall
     

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  2. jcsd
  3. Oct 23, 2013 #2
    What are these F, F1, F2? A diagram would be useful.
     
  4. Oct 23, 2013 #3
    sry i was just uploading the diagram . my apologies
     
  5. Oct 23, 2013 #4

    ZapperZ

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    1. This is vague. You need to show in a sketch what you mean by "F1 and F2".

    2. This is a rather common problem in statics. Have you tried it yourself? Have you tried looking it up? It took me less than 5 seconds to find this:

    http://farside.ph.utexas.edu/teaching/301/lectures/node133.html

    Edit: I see a sketch now.

    Zz.
     
  6. Oct 23, 2013 #5
    i just uploaded the diagram , i forgot to upload when i first posted the thread
    and mr zapper , i have seen your link , there is only a friction force on the horizontal direction , i mean there should be a force by the ladder , because of there is no force by the ladder on the ground then there should be no friction
     
  7. Oct 23, 2013 #6

    ZapperZ

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    OK, so why can't you add that vertical friction?

    Presumably, from the way you responded, you already know how to solve the problem with only the horizontal friction at the bottom of the ladder. What is the difficulty in adding another vertical friction at the top of the ladder?

    BTW, you really should show the free-body diagram in full. The diagram you showed doesn't show much of what you've understood in solving this problem.

    Zz.
     
  8. Oct 23, 2013 #7
    i am currently studying general equilibrium of bodies ,
    i can solve it with both frictions , but the thing is , how does horizontal friction arise if the ladder does not act with a force on the ground ?
    in the link you sent me , as you can see , on the ground , there is a horizontal force of Friction , but on the other hand , there is no other force opposing it , there should be a force caused by the ladder on the ground which caused friction to arise
    the only horizontal force that opposes the horizontal friction on the ground is the Reaction by the wall on the ladder denoted by S in the diagram in your link , is this force S what causes friction to arise on the ground ?
    if it is , then why would increasing the weight increase the horizontal friction ?
    as far as i could tell weight will not affect the Force S which is the reaction of the wall
     
  9. Oct 23, 2013 #8
    In a free body diagram for the ladder you show only the forces on the ladder. Not on the ground, the wall or other objects. This is what they did in that link.
    But there are forces on the wall and on the ground.
    Actually what you showed in your diagram are some of these forces and not the ones on the ladder.
     
  10. Oct 23, 2013 #9
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