# When a ship is said to be Equilibrium,Stable,Unstable And Neutral equilibrium

Equilibrium

When the ship is in upright position, the force of buoyancy(up thrust) and the force of gravity(weight) acts through the center of buoyancy B and the Center of gravity G respectively, in the same vertical line. Then the ship is said to be in equilibrium.

Stable
When the ship's metacenter M lies above the center of gravity, then the vessel is stable Ie, GM is positive.Here the force of buoyancy acts upwards through metacenter and the Force of gravity acts through center of gravity, thereby creating a momentum which tends to right the ship.

Unstable
When the ship's metacenter lies below the center of gravity, the moment acts in the opposite direction, increasing the angle of heel. Hence , the vessel will not return to the upright position.Then the vessel is said to be unstable ie, GM is negative

Neutral equilibrium

When the ship's metacenter and center of gravity coincide at same point then the vessel is said to be neutral equilibrium. There is no moment acting on the ship so it remains inclined.