Quantitative Reasoning

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  • PE1.7
  • March 4, 2015 at 2:00 pm #29672

    Ezra Halleck
    Participant

    7. In Karate, the force needed to break a board varies on inversely with the length of the board. If it takes 10 lb of force to break a board that is 2 feet long. How much force is needed to break a 5 ft board?
    Define 2 variables, write an equation and identify the constant of proportionality.

    March 12, 2015 at 9:27 pm #29844

    Meizhu Deng
    Participant

    let L=length of the board 5ft.
    f= force needed to break the 5ft board.
    k= the constant proportionality.
    f=k/L= k/5
    since 10lb needed to break 2ft board
    10=k/2 k=20
    substitute k=20 into equation f=k/5 ; f=20/5=4 (lb)
    4lb is needed to break 5ft long board.

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