What is Centre of Gravity & where to find it in some regular objects easily?
Last updated on December 30th, 2021 at 12:33 pm
In this post, we’ll first discuss what the Centre of Gravity is. And then we’ll quickly list down where to find the centre of gravity in some regular objects easily.
In simple words, the centre of gravity of a body is the point where the whole weight of the body can be considered to act.
The centre of gravity of a body may even lie outside the actual material of the body. For example, the centre of gravity of a ring lies at its centre, which is outside its material.
Centre of gravity of a rigid body – understanding in details with diagram
Consider a rigid body. It consists of a number of particles and these particles are attracted towards the earth due to gravity.
The forces acting on the particles are F1, F2, F3, etc. These forces act downwards along parallel lines. (Actually, these forces denote the weight components contributed by the particles.) These parallel forces can be replaced by a single force whose effect is the same as the combination.
This single force is the resultant of all the downwards forces. The resultant force acts at a particular point. This point can be assumed as the point where the whole weight, W of the body acts. This point is known as the centre of gravity (C.G)
One more vital point: This C.G. point has another important characteristic. If moments (moment of force) of all the downward weight forces (from all particles) are calculated with respect to the C.G. of the object and then algebric sum of these moments is calculated then the result will be zero.
Define Centre of gravity | Definition
The Centre of Gravity (C.G.) of a body is the point about which the algebric sum of moments of weights of particles constituting the body is zero and the entire weight of the body is considered to act at this point.
Location of Centre of Gravity in some regular objects
This is a tabular list of regular objects and the position of CG for each of them.
| Object | Position of Centre of Gravity |
|---|---|
| Rod | at the Midpoint of the rod |
| Circular Disc | at the Geometric centre |
| solid or hollow sphere | at the geometric centre of the sphere |
| cylinder | at the midpoint on the axis of the cylinder |
| circular ring | at the centre of the ring |
| triangular lamina | at the point of intersection of the medians |
| parallelogram-shaped lamina | at the point of intersection of the diagonals |
| rectangular lamina | at the point of intersection of the diagonals |
| square lamina | at the point of intersection of the diagonals |
| solid cone | It is at a height h/4 from the base, on its axis. (h = height of cone) |
| hollow cone | It is at a height of h/3 from the base, on its axis. (h = height of cone) |
FAQ
Where is the Centre of Gravity in a Rod?
It is at the midpoint of the rod.
Where is the Centre of Gravity in a Circular Disc?
It is at the geometric centre.
Where is the Centre of Gravity in a solid or hollow sphere?
It is at the geometric centre of the sphere.
Where is the Centre of Gravity in a cylinder?
It is at the midpoint on the axis of the cylinder.
Where is the Centre of Gravity in a circular ring?
It is at the centre of the ring.
Where is the Centre of Gravity in a triangular lamina?
It is at the point of intersection of the medians.
Where is the Centre of Gravity in a parallelogram-shaped lamina?
It is at the point of intersection of the diagonals.
Where is the Centre of Gravity in a rectangular lamina?
It is at the point of intersection of the diagonals.
Where is the Centre of Gravity in a square lamina?
It is at the point of intersection of the diagonals.
Where is the Centre of Gravity in a solid cone?
It is at a height h/4 from the base, on its axis. (h = height of cone)
Where is the Centre of Gravity in a hollow cone?
It is at a height of h/3 from the base, on its axis. (h = height of cone)
