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Math Help - vectors

  1. #1
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    vectors

    an object P is acted upon by 3 coplanar forces one force is a hundred pounds due south another is 150 pointing due east and the third is 200 lbs 30 degrees north of east. What is the force needed to prevent P from moving
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  2. #2
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    Hello, leinadwerdna!

    Do you know how to write vectors and add vectors?


    An object P is acted upon by 3 coplanar forces.
    One force is 100 pounds due south,
    another is 150 pounds due east
    and the third is 200 pounds 30 north of east.
    What is the force needed to prevent P from moving?
    Code:
                              w
                            *
                  200   *
                    *
            P   * 30
            o - - - - - - * v
            |     150
        100 |
            |
            *
            u

    We have: . \begin{array}{ccc} \vec u &=& \langle 0,\:\text{-}100\rangle \\<br />
\vec v &=& \langle 150,\:0\rangle \\<br />
\vec w &=& \langle 100\sqrt{3},\:100\rangle \end{array}


    The resultant vector is: . \vec u + \vec v + \vec w \;=\;\langle 250\sqrt{3},\:0\rangle

    P is moving directly east with a force of 250\sqrt{3} pounds


    To prevent movement, 250\sqrt{3} pounds of force must be applied directly west.
    . . The applied vector would be: . \langle \text{-}250\sqrt{3},\:0\rangle

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  3. #3
    Member eXist's Avatar
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    Shouldn't this:
    Quote Originally Posted by Soroban View Post

    The resultant vector is: . \vec u + \vec v + \vec w \;=\;\langle 250\sqrt{3},\:0\rangle
    Be this?
    \vec u + \vec v + \vec w \;=\;\langle 150+100\sqrt{3},\:0\rangle
    Last edited by eXist; January 23rd 2010 at 08:41 PM.
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  4. #4
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    the answer in the book is 323 lbs due west not equivalent to either of the answers u two gave. what is wrong
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  5. #5
    Member eXist's Avatar
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    I edited my previous post. Check the answer now, it should be correct.
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  6. #6
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    ok i get that but how do u know the force must be applied due west to stop the object
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