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Daily Question for Feb. 19, 2018

ship is inclined by moving a weight of 30 tons a distance of 30 ft. from the centerline. A 28-foot
pendulum shows a deflection of 12 inches. Displacement including weight moved is 4,000 tons.
KM is 27.64 feet. What is the KG?

A. 21.34 feet

B. 22.06 feet

C. 22.76 feet

D. 23.21 feet

Comments

  1. UnknownFebruary 19, 2018 at 5:02 PM

    George I'm in need of a lesson on this one .

    ReplyDelete
  2. Friends of STABILITY AND TRIM FOR THE SHIP'S OFFICERFebruary 19, 2018 at 7:13 PM

    To answer this you need the Inclining Experiment Formula (Go back to The Daily Question for Feb. 10, 2018)

    Tangent of angle of list =
    (inclining weight in tons x distance weight moved in feet)/(GM in feet x Displacement in Long Tons)

    In a previous post I derived the Inclining Experiment Formula as follows:

    Derivation of Inclining Experiment Formula
    If any weight is shifted on board a vessel, the center of gravity of the vessel will shift in a direction parallel to the weight movement. The distance G moves is found by the formulas:
    1. GG' = (w x d) / Displ. (this is the transverse shift in G)

    2. tan (angle of list) = GG'/ GM
    [See Figure 6-2 D in the book or image the triangle formed]

    3. GG' = GM tan (angle of list)
    [transposing equation (2.) to solve for GG']

    4. GM tan (angle of list) = (w x d) / Displ.
    [(setting equation (3.) equal to (1.)]

    5. GM = (w x d) / (Displ.)(tan (angle of list))
    [ Solving for GM, we get the Inclining Experiment Formula!]

    So to solve this question you need to know the Inclining Experiment Formula and that
    KM - KG = GM, so you can solve for KG after you determine GM from the Inclining Experiment Formula.

    First let us find GM = wd/Displacement(tan of angle of list)

    We really do not need the angle of list just the tangent function of that angle which is has been defined and given by the length of the pendulum and the deflection of the pendulum

    Tangent of the angle of list = deflection / length of pendulum
    = 1 foot /28 feet = 0.035714

    Now we can solve by transposing the equation and solve for GM

    GM = wd/Displacement (tan of angle of list)
    GM = 30 tons x 30 ft / 4000 tons (0.35714) = 6.30 feet

    KG= KM - GM = 27.64 ft - 6.30 ft = 21.34 ft

    So Choice A is the best answer.

    Do you think it is fair to have questions that test more than one thing to find the answer? In this problem I counted at least three things you needed to know and/or do.

    ReplyDelete
  3. UnknownFebruary 24, 2018 at 5:24 AM

    DOUBLE ROGERS -- THE INCLINING EXPERIMENT !

    chapter 6 pg. 111


    GM= W*D / displacement*(tan of angle of list) -- FYI (tan=Opposite/Adjacent)

    30*30=900

    4000*(1/28)=142.8571429 ---- BTW(1/28=0.035714286)

    900/142.8571429= 6.3=GM

    KG=KM-GM ---- KM is given KM= 27.64

    27.64-6.3=21.34

    ANS: ALPHA

    stay the course dav c keep working these you'll get it !

    ReplyDelete

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