Question 64 RVR05 - Master of LT 100 GRT

The Correct Answer is A ### 2. Explanation of Option A **A) By dividing the trim moments by MT1** This option provides the correct and standard formula used in ship stability calculations to determine the resultant change in trim. * **Trimming Moment:** This is the force created by shifting weight longitudinally or adding/removing weight at a longitudinal distance from the Longitudinal Center of Gravity (LCG). It is calculated as Weight (W) $\times$ Distance (d). * **MT1 (Moment to Change Trim by 1 unit):** Also commonly referred to as MTC (Moment to Change Trim by 1 cm/inch), this value represents the longitudinal stability of the vessel. It is the moment required to change the overall trim of the vessel by one unit of measure (e.g., 1 centimeter). * **The Formula:** $\text{Change in Trim} = \frac{\text{Total Trimming Moment}}{\text{MT1 (or MTC)}}$ Dividing the total longitudinal moment applied by the vessel's resistance to trimming (MT1) yields the total resulting change in trim. --- ### 3. Explanation of Incorrect Options **B) By subtracting the LCF from the LCB** * **Incorrect:** LCF (Longitudinal Center of Flotation) is the center of the waterplane area, and LCB (Longitudinal Center of Buoyancy) is the center of the underwater volume. The distance between these two points is a hydrostatic property of the vessel's shape at a given draft. It is used in stability calculations (and is related to the initial trim caused by the distance between LCG and LCB), but it does not calculate the resulting *change* in trim due to a weight change or shift. **C) By dividing longitudinal moments by the displacement** * **Incorrect:** Dividing the total longitudinal moment (Moment about the Midships or some datum) by the displacement (total weight of the vessel) calculates the position of the Longitudinal Center of Gravity (LCG) relative to that datum line. This calculation determines where the gravity force acts, not the resulting change in the vessel's trim angle. **D) By looking at the Hydrostatic Properties Table for the draft of the vessel** * **Incorrect:** The Hydrostatic Properties Table lists values (such as MTC/MT1, Displacement, LCB, LCF) that are *required* to perform stability calculations. These tables describe the condition of the vessel at a given even-keel draft. The *change in trim* is a resultant value that must be calculated based on a specific load alteration; it is not a fixed value found directly in the table.