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Tension Q

  1. Oct 13, 2005 #1
    theres two blocks

    a 4 KG one and a 5 KG one right next to each other, connected by a c ord, the 5 KG is on the right and its conected to another cord pulling 30 N to the right.


    Box1----Box2----30 N
    get it
    so theyre asking for the tension in the cord connecting them
    it slipped my mind how to do this :(
    i got acceleration of the system to be 3.3 m/s tho
  2. jcsd
  3. Oct 13, 2005 #2


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    Did you draw the FBDs?
  4. Oct 13, 2005 #3
    yes i did
    but im confused really
    i know its a simple questoin
    test is 2morrow
  5. Oct 13, 2005 #4


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    Ok then let me see your equations for each body
  6. Oct 13, 2005 #5
    well for acceleration

    i did

    9a = 30
    and got 3.33 m/s, which was right
    now they ask for tension of cord connecting them, i just hit a blank spot here for some reason.
    lets say i make a fbd for the 5 kg box, so it got 30 N going one way, and the other way? is it 4 x10? no right. and theres no friction btw
    i cant think, relaly, just help me out, im not trying to get u guyst od o my hw or antyhign honeslty, this is jsut a review Q for a test tmorrow!
  7. Oct 13, 2005 #6


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    Explain how you got a. Also, consider the following:

    1. What force is acting on the left block?
    2. What can you say about the relationship between the acceleration of block 1 and the acceleration of block 2
    3. What equations of motion are you using?
  8. Oct 13, 2005 #7


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    Basicly you considered your system the whole 2 boxes, that's ok, but then the tension force will be an internal force instead of an external force, analyze for each body in order to find the tension.
  9. Oct 13, 2005 #8
    k got the asnwer
    sorry for the stupidness
    i had some brain crmap or something :D
  10. Oct 16, 2005 #9
    Further thought to the above question by SS2006, can I know how come everytime we draw a FBD, the rope has force in both opposite direction

    box 1 -- box 2---
    for the -- between the box1 and 2, the direction of force is box1--<-->--box2--30N
    *the arrow shown is for the tension of the rope only
    hope you get what I mean:)
    Last edited: Oct 16, 2005
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