A ship of 3000 tonne displacement has 500 tonne of cargo on board. This cargo is lowered 3 m and an additional 500 tonne of cargo is taken on board 3 m vertically above the original position of the centre of gravity. Determine the alteration in position of the centre of gravity.

A ship of 3000 tonne displacement has 500 tonne of cargo on board. This cargo is lowered 3 m and an additional 500 tonne of cargo is taken on board 3 m vertically above the original position of the centre of gravity. Determine the alteration in position of the centre of gravity.

Reference: REED'S NAVAL ARCHITECTURE FOR MARINE ENGINEERS (4^th edition), Exercise – 4.5

 

Solution:

Shift in KG = mass moved*distance moved/displacement

                   = 500*3/3000

                   = 0.5 m down

Mass (ton)	KG (m)	Moment (ton-m)
3000	0	0
+500	3.5	1750
∑ = 3500		∑ = 1750

 

New KG = moment/mass

               = 1750/3500

               = 0.5 m up

The position of the center of gravity doesn’t change.