Center of Gravity

Center of Gravity

The center of gravity is the point at which the whole weight of a body is considered to act.

To determine the center of gravity (c.g) of an irregular plane lamina.

Stick the lamina through with a pin close to one edge, (point A)

Stick the pin into a piece of cork and clamped the cork using a retort stand

Ensure that the lamina hangs freely

Tie a plumb-bob onto the end of the pin so that it hangs in front of the lamina.

Mark the opposite end of the lamina where the plumb bob touches, (point B)

Dismount the lamina and draw a line connecting the point of suspension to the opposite end i.e connect point A to point B.

Repeat this procedure twice using different edges as the starting point.

Mark the point of intersection of the three lines

This point is the center of gravity.

The center of gravity of geometric, uniform objects is found at the geometric center.

View a short simulation about center of gravity here

Try it out

Cut out a piece of cardboard that's roughly this shape, or try printing this image and tracing it in cardboard. (I'm not sure how large the print will come out, but you can try it. It should be roughly the size of A4 paper or even half A4 will work). Follow the procedure above the find the centre of gravity of the lamina.

Toppling

Toppling occurs when the center of gravity acts outside the base of an object. It's stability depends on

i) the height of the center of gravity above the base; the higher the c.g the easier the object can topple

ii) the area of the base. The broader the base the more difficult for the object to topple

View this video that talks explains why objects topple