1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Need help with this lever problem

  1. Oct 12, 2012 #1
    Please help me guys, I joined this forum just to post this... spent an hour or so trying to get the answers but I cant for the life of me!

    1. The problem statement, all variables and given/known data

    http://imageshack.us/a/img141/9812/20121012003953.th.jpg [Broken]

    2. Relevant equations


    3. The attempt at a solution

    http://imageshack.us/a/img211/7388/20121012003920.th.jpg [Broken]
    1. The problem statement, all variables and given/known data



    2. Relevant equations



    3. The attempt at a solution
     
    Last edited by a moderator: May 6, 2017
  2. jcsd
  3. Oct 12, 2012 #2

    Simon Bridge

    User Avatar
    Science Advisor
    Homework Helper
    Gold Member
    2016 Award

    Summarizing the problem in text avoids making people squint at photographs.

    33m beam has two supports
    overhangs both by 5m
    600kN at extreme right end
    900kN at extreme left end
    159kN/m over entire length
    Calculate support reactions.
    ...

    You seem to have worked the torques...
    Where did you get stuck? Work slowly through the math - showing your reasoning.
     
  4. Oct 12, 2012 #3
    I dont know where im getting stuck, but I aint getting the answer. Im not sure what im doing wrong.. ive tried so many different combinations.. obviously the basis for the formula is clockwise movements=counterclockwise movements, but I aint getting the answer.. and 900kN is not at the extreme left end, its 8m from the left end.
     
  5. Oct 13, 2012 #4

    Simon Bridge

    User Avatar
    Science Advisor
    Homework Helper
    Gold Member
    2016 Award

    Oh I misread that - see the problem with presenting the problem in a photograph?

    I'm having trouble treading your working in the photo - I see a 900x8 in there ... that would be the torque about the extreme left end from the 900kN point force. But there is no pivot there: the pivot is 5m, in from that end.

    You can reality check your answer by noticing that the total downward force has to equal the total upward force (the beam ain't going anywhere.)

    Mind you - taking a look at the answers they give (3297kN and 3453kN) I see they add up to 6750kN upwards... the total downwards force is 6747kN, suggesting that the beam will lift off under a net unbalance 3kN.

    I think the distributed force was supposed to be 159.09kN/m ... and somebody rounded off when they shouldn't have.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: Need help with this lever problem
  1. Farmer Lever problem (Replies: 2)

  2. Lever Problem (Replies: 8)

  3. Lever problem (Replies: 6)

  4. Lever problem (Replies: 1)

Loading...