What is the longitudinal shift in the center of gravity if 200 short tons is moved ten feet to port and 30 feet forward on a MODU with a displacement of 8,960 long tons?
• Transverse and longitudinal shift of center of gravity (GG') on a vessel or MODU • Using the moments formula: shift of G = (weight moved × distance moved) ÷ total displacement • Distinguishing between short tons vs long tons and when they matter in the calculation
• How do you combine a move to port and a move forward when you are asked for the longitudinal shift only? • Which distance (10 ft to port or 30 ft forward) should be used in the numerator when calculating the longitudinal movement of G? • After computing GG', is the answer likely to be a small fraction of a foot or several feet, given that the ship’s displacement is very large compared with the weight moved?
• Be sure you are using the displacement in the same units of weight as the weight moved, or recognizing when the ratio makes the unit type cancel out • Check that you used only the longitudinal distance (forward/aft) when asked for longitudinal shift, not the transverse distance • Verify that your final GG' value is reasonable in magnitude given the relatively small weight (200 tons) compared with the large displacement (8,960 tons)
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