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Diagram of the see-saw and parallel mirrors

  1. Nov 25, 2006 #1
    1. Two mirrors are placed parallel to each other on a sea-saw. A beam incident in analmost vertical plane, on the first mirror is reflected to be incident on the second and then is further reflected to form a spot on the wall at some distance away. If the sea-saw is turned through an angle theta, through what angle will the reflected beam turn?

    2. If for two vectors A and B; |A+B|=|A-B| then

    a) |A-B|=|A|+|B|
    b) |A+B|=|A|-|B|
    c) |A+B|=0
    d) |A.B|=0

    Please let me explai, I have no idea about these questions. Please explain it to me. I have astonomy olympiad so I got them by reading the past papers.
  2. jcsd
  3. Nov 25, 2006 #2


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    Staff: Mentor

    In the first problem, it would be useful to draw a diagram of the see-saw and parallel mirrors.

    In the second problem |A| means magnitude of vector A.

    The problem asks for the meaning of the statement 'the magnitude of the vector sum of vectors A and B = magnitude of the vector difference of A and B. How is this possible? What other condition is inferred?
  4. Nov 25, 2006 #3
    Please sir, try to be clear. I cant grasp things of that level like that. I am just at the 9th standard (14 yrs. old)
  5. Nov 26, 2006 #4


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    Science Advisor
    Homework Helper

    Take a piece of paper and draw two vectors A and B such that the sum of the two vectors A + B has the same length as the difference between the vectors A - B. Which of the four answer conditions is statisfied by these two vectos?
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