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Daily Question for Jan 20, 2018

Metacentric height is a measure of __________.

A. initial stability only

B. stability through all angles

C. maximum righting arm

D. All of the above

Comments

  1. Yuri PantojaJanuary 20, 2018 at 7:09 AM

    Leter A.

    Not all angles, just small angles (0-15)
    Maximum Righting Arm is the maximum possible moment applied to the ship without causing it to capsize.

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  2. UnknownJanuary 20, 2018 at 2:09 PM

    I too believe it's A. Only for small angles of incline.

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  3. UnknownJanuary 20, 2018 at 2:19 PM

    GM is a measure of initial statical stability up to angles of about 10 degrees

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  4. Friends of STABILITY AND TRIM FOR THE SHIP'S OFFICERJanuary 20, 2018 at 7:28 PM

    A. is the best answer. GM is Metacentric Height, and is really only good for small angles of heel, I say no more than 8 degrees and is really just a simple "yard stick" to measure a vessel's stability. Keep in mind a vessel's Stability is a Tendency to return to its initial condition when disturbed by an external force. It actually resembles pendulum motion and is sometime referred to as Pendulum Stability. It has been said that if a vessel has an adequate GM it "SHOULD SURVIVE" in the open ocean.

    As you go to larger angles of heel, (not list!), GZ and Righting Moment are the true measure of how a vessel will respond to an external force such a wind, or lifting a weight with the vessel's cargo gear, or pumping ballast or liquid cargoes. Keep in mind you can use GZ and Righting Moment for small angles of heel also, however GM is used because it is simpler. (WHY? Because KM-KG=GM, all the math is done on a number line by simple subtraction that an 8 year old should be able to do!) So the the initial GZ slope of a stability curve is approximated by
    GZ =GM x (sine of the angle of heel)
    as a straight line segment from 0 to about 8 to 10 degrees.

    Choice B. can easily be ruled out because GM only applies to small initial angles of heel.

    Choice C. Maximum Righting Arm occurs near deck edge immersion. With adequate freeboard required by the Loadline Regulations this should be an angle larger than 8 to 10 degrees.

    Choice D. is rarely employed as a correct answer, although there are a few question that may have "All of the above." as a correct answer. This is just a "distractor" to try to trick you.

    Hint! when reading these multiple choice questions CAREFULLY treat each choice as a True or False question.

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  5. UnknownJanuary 22, 2018 at 2:37 AM

    A. The vertical distance of GM. Used as the measure of initial stability.

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