A ship is said to be in stable equilibrium

A ship is said to be in stable equilibrium if its center of gravity (CG) is located below its metacenter (M), and its metacentric height (GM) is positive. This means that when the ship is heeled (i.e., tilted to one side), the restoring force that acts on the ship is greater than the destabilizing force. As a result, the ship will return to its upright position on its own once the disturbing force is removed.

In other words, if the ship is heeled to one side, the buoyancy force acting on the submerged portion of the hull will shift to the opposite side of the center of gravity, creating a torque that tries to return the ship to its upright position. The magnitude of this torque depends on the metacentric height, which is a measure of the distance between the center of gravity and the metacenter.

If the center of gravity is located above the metacenter, the ship will be in unstable equilibrium, which means that it will not return to its original position on its own but will continue to heel until it capsizes. If the center of gravity is located at the same level as the metacenter, the ship will be in neutral equilibrium, which means that it will remain at its new position after being heeled without any restoring force acting on it.

In summary, a ship is said to be in stable equilibrium if its center of gravity is located below its metacenter, and its metacentric height is positive. This state ensures that the ship will return to its upright position on its own once it is heeled, making it safe and stable in rough seas and high winds.

By capt. NJS