Results 1 to 6 of 6

Thread: statics

  1. #1
    Junior Member
    Joined
    Aug 2017
    From
    England
    Posts
    57

    statics

    i am stuck on question 9

    statics-win_20170817_17_32_04_pro.jpgClick image for larger version. 

Name:	WIN_20170817_17_32_04_Pro.jpg 
Views:	12 
Size:	169.7 KB 
ID:	37990

    i am not sure where the forces are and there directions.

    thanks
    Follow Math Help Forum on Facebook and Google+

  2. #2
    Junior Member
    Joined
    Aug 2017
    From
    England
    Posts
    57

    Re: statics

    statics-img_20170818_100307100.jpgClick image for larger version. 

Name:	IMG_20170818_100307100.jpg 
Views:	6 
Size:	863.3 KB 
ID:	37998

    Does anyone know if my forces in this diagram are right?
    Am I missing any?
    Follow Math Help Forum on Facebook and Google+

  3. #3
    MHF Contributor

    Joined
    Apr 2005
    Posts
    19,462
    Thanks
    2893

    Re: statics

    There are forces perpendicular to the rods at the points of contact with the disk but the vectors should be pointed toward the rods, not away from them. Of course, since this is in equilibrium, there is an equal force acting on the disk pointing the way you have it but since the question asked is about the tension in the string, it is the force on the rods you want to find. The vertical component of force on each is W/2. You have three vectors marked "W". Why are there three? The tension forces in the rods are in the direction of the rods and the forces at each end of the extensible string are in the horizontal direction of the string.
    Follow Math Help Forum on Facebook and Google+

  4. #4
    Junior Member
    Joined
    Aug 2017
    From
    England
    Posts
    57

    Re: statics

    i dont see why you think the "forces perpendicular to the rods at the points of contact with the disk but the vectors should be pointed toward the rods, not away from them". in all the worked examples in my book the normal reaction always reacts away from the point of contact towards the object (the disc). how are you supposed to know what direction the normal reactions go in. Is there a rule?

    there is no tension in the rods. there is tension in the string. both of the rods are of weight w so w acts downwards for both rods. the disc is also of weight w so this also acts downwards.


    in the question its says the rods are freely hinged at o. will there be any forces at this.? usually when something is hinged in a question I was told to split it up into x and y components.
    Follow Math Help Forum on Facebook and Google+

  5. #5
    Junior Member
    Joined
    Aug 2017
    From
    England
    Posts
    57

    Re: statics

    i understand a bit more now. so you get equations by looking at 3 parts of the question . forces on rod ab,forces on rod cd and forces for the whole system. for the whole system i let forces up=forces down and forces right=left. i am now looking at forces on the rods individually. i am still stuck though

    here is updated diagram

    statics-win_20170818_15_05_10_pro.jpgClick image for larger version. 

Name:	WIN_20170818_15_05_10_Pro.jpg 
Views:	2 
Size:	87.6 KB 
ID:	37999
    Follow Math Help Forum on Facebook and Google+

  6. #6
    MHF Contributor ebaines's Avatar
    Joined
    Jun 2008
    From
    Illinois
    Posts
    1,389
    Thanks
    420

    Re: statics

    From sum of forces in the vertical direction you can figure the reaction forces S1 and S2. Then from sum of torques about the hinge point O = zero for either rod you can determine the tension in the string. Try it, and post back with your attempt.
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Statics
    Posted in the Advanced Applied Math Forum
    Replies: 2
    Last Post: Aug 9th 2017, 10:04 AM
  2. statics
    Posted in the Advanced Applied Math Forum
    Replies: 5
    Last Post: Apr 25th 2017, 11:52 PM
  3. Statics
    Posted in the Advanced Math Topics Forum
    Replies: 2
    Last Post: Mar 8th 2017, 04:08 AM
  4. Statics
    Posted in the Trigonometry Forum
    Replies: 1
    Last Post: Aug 21st 2009, 06:14 AM
  5. STatics Help!!
    Posted in the Advanced Applied Math Forum
    Replies: 1
    Last Post: Feb 20th 2009, 03:55 AM

/mathhelpforum @mathhelpforum