Algebra 2 help please?!?

the period of a pendulum is the time the pendulum takes to swing back and forth. the function l=0.81(squared) relates the length l in feet of the pendulum to the period l.

A. If a pendulum is 30 feet long, what is the period of the pendulum in seconds?

B. why does only one of the solutions work for this problem?


the variables are all L

2 Answers

  • Anonymous
    9 years ago
    Favorite Answer

    T= 2*Pi*(L/g)^(1/2)

    A. This means that if the pendulum is 30 ft. long the solution is about 6 seconds to oscillate.

    B. Since L is the only variable that is present, (g is gravity) there can only be one answer for when one lenght is given.

    This is a correct answer. I am not sure how you can relate L=.81^2 to L. There are no variables.

  • Ian H
    Lv 7
    9 years ago

    You can do easy questions like this if you just concentrate and try properly.

    Probably it seemed harder because you missed a bit when you copied the question.

    It should have been

    L = 0.81*T^2 (otherwise it makes no sense).

    A. There is no mystery to this, you hardly have anything to do,

    just put 30 where it said L and you get

    30 = 0.81*T^2

    rearrange to find T

    (remembering that a square root has two solutions one positive and one negative)

    T = sqrt(30/0.81) ~ 6.086 or -6.086

    B. Since time only goes forward a period of about minus 6 seconds

    does not make much sense so only the positive solution works.

    Now I hope you see how easy it was.

    Regards - Ian

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