Centre of Gravity (Edexcel IGCSE Physics (Modular))

Centre of gravity

• The centre of gravity of an object is defined as:

The point through which the weight of an object acts

• For a symmetrical object of uniform density, the centre of gravity is located at the point of symmetry

  • For example, the centre of gravity of a sphere is at the centre

Finding the centre of gravity of symmetrical objects

The centre of gravity of a regular shaped object can be found using symmetry

• The centre of gravity of an irregular object can be found using suspension

• The irregular shape is suspended from a pivot and allowed to settle

• A plumb line (weighted thread) is then held next to the pivot and a pencil is used to draw a vertical line from the pivot (the centre of mass must be somewhere on this line)

• The process is then repeated, suspending the shape from two additional points

• The centre of mass is located at the point where all three lines cross