LESSON 2B

The term “stability” Usually refers to:

• the ability of a vessel to maintain an upright position when being acted upon by external forces.

• the ability of a vessel to return to an upright position after being heeled by an external force.

• the ability of a vessel to be loaded to her maximum capacity and maintain seaworthiness.

• the ability of a vessel to resist the actions created by external forces.

Longitudinal stability refers to:

• the trim and pitching of a vessel.

• the side to side rolling of a vessel.

• isochronous rolling.

• hogging and sagging

The perpendicular distance between “G” and the direction of the action of the force of buoyancy is called:

• the righting lever (GZ)

• the metacentre (M)

• the center of buoyancy (B)

• the center of gravity (G)

List is normally caused by:

• weights being added high in the vessel

• weights being added low in the vessel

• external forces acting on the hull of the vessel

• weights being shifted transversely.

A vessel is said to be heeled when she is:

• laid over to one side so that work may be done on the opposite side.

• on a slipway and blocks are secured under her hull to keep her upright.

• rolled to one side or the other when acted on by wind and/or sea.

• heavy laden with ice.

If a vessels center of gravity is above the metacentre the vessel is said to be in:

• stable equilibrium

• neutral equilibrium (have zero GM)

• unstable equilibrium (have a negative GM)

• a lolled condition.

What would the ship’s stability condition be if the center of gravity coincided with the metacentre?

• The ship would have excessive stability

• The ship would be in a condition of neutral equilibrium.

• The ship would have positive GM.

• The ship would have a negative GM.

Why is the metacentric height a measure of the vessel’s initial stability?

• Because the size of the metacentric height is proportional to the righting lever at a given moderate angle of heel.

• Because the metacentric height is related to the the height of the metacentre above the center of buoyancy.

• Because the metacentric height is directly related to the position of the center of gravity.

• Because the greater the metacentric height the larger is the initial stability.

The angle of loll is described as:

• the angle at which a vessel having a negative GM will rest.

• the angle at which a vessel having zero GM will rest.

• the angle at which a vessel having positive GM will rest.

• the angle at which the vessel heels in a seaway.

When a vessel in unstable or neutral equilibrium is to be made stable the center of gravity has to be lowered. Which of the following would be an effective way of lowering a vessel’s center of gravity?

• Weights already in the vessel may be lowered.

• Weights may be loaded below the center of gravity.

• Weights may be discharged from positions above the center of gravity.

• All of the above.