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Math Help - Scalar, Vector, Meaningless

  1. #1
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    Scalar, Vector, Meaningless

    State whether the following expressions are vectors, scalars, or meaningless.

    I need help with these two.. I think personally, that my answers are right, but perhaps my reasoning is not valid because the back of the book has a diff answer.

    Here is what I am thinking:

    a) (a x b) + (b x c)
    =vector + vector
    =scalar
    I say the answer is scalar because for example
    (4,3,2) + (2,1,2)
    =6+4+4
    =14<<<< scalar
    But the back says vector, what am i missing here?

    b) (a x b) - c
    =vector - vector
    =scalar
    I say the answer is scalar because for example
    (1,2,3)-(3,2,1)
    =-2+0+2
    =0<<< scalar
    But the back says vector, what did i do wrong here?

    c) (a . b) - c
    =scalar - vector
    =scalar
    I say the answer is scalar because for example
    4-(4,3,2)
    =4(-4,-3,-2)
    =-16-12-8
    =-36 <<< scalar
    what did i do wrong here and what should the answer be?


    Note: bolded are vectors
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  2. #2
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    Quote Originally Posted by skeske1234 View Post
    State whether the following expressions are vectors, scalars, or meaningless.

    I need help with these two.. I think personally, that my answers are right, but perhaps my reasoning is not valid because the back of the book has a diff answer.

    Here is what I am thinking:

    a) (a x b) + (b x c)
    =vector + vector
    =scalar NO it is a vector.
    I say the answer is scalar because for example
    (4,3,2) + (2,1,2)
    =6+4+4
    =14<<<< scalar NO it is a vector.
    But the back says vector, what am i missing here?

    b) (a x b) - c
    =vector - vector
    =scalar NO it is a vector.
    I say the answer is scalar because for example
    (1,2,3)-(3,2,1)
    =-2+0+2
    =0<<< scalar NO it is a vector.
    But the back says vector, what did i do wrong here?

    c) (a . b) - c
    =scalar - vector
    =scalar NO it is meanless.
    I say the answer is scalar because for example
    4-(4,3,2)
    =4(-4,-3,-2)
    =-16-12-8
    =-36 <<< scalar
    what did i do wrong here and what should the answer be?


    Note: bolded are vectors
    The sum or difference of vectors is always a vector.
    The cross product of two vectors is a vector.
    The dot product of two vectors is a scalar.
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