A jack-up 210 feet in length is level during transit. The LCF is 140 feet aft of the bow. How much weight should be applied at the bow to level the jack-up if 150 kips are loaded at the transom?
• Lever arm / moment = force × distance about the Longitudinal Center of Flotation (LCF) • A jack-up that is "level during transit" means the net trimming moment about LCF is zero • Distances forward of LCF are taken with opposite sign to distances aft when summing moments
• Where is the 150-kip load located relative to the LCF, in feet and in what direction (forward or aft)? • What trimming moment does that 150-kip load create about the LCF, and what equal and opposite moment must the bow load create? • Given the bow is on the opposite side of the LCF from the transom, how does that affect the sign of its distance and the weight needed to balance moments?
• Compute the distance from LCF to transom using the vessel length and LCF location; keep track of which side is forward/aft. • Write a simple moment-balance equation: sum of moments about LCF = 0; use one unknown (bow weight). • Before choosing an answer, confirm that the units (kips × feet) are consistent and that the direction of each moment (bow vs stern) is correctly assigned.
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