Finding the Centre of Mass (Oxford AQA IGCSE Physics)

Finding the Centre of Mass

• The centre of mass of an object is

The point in an object at which the mass can be thought to be concentrated

• For a symmetrical object of uniform density (such as a symmetrical cardboard shape), the centre of mass is located at the point of symmetry

  • The shape needs to have more than one line of symmetry

Centre of mass of a symmetrical object

• For non-symmetrical objects, the centre of mass can be found using suspension

• When an object is suspended from a point, the object will always settle with its centre of mass directly below the point of suspension

Centre of mass of a non-symmetrical object

• The irregular shape (also called a plane lamina or thin lamina) 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