Centre of Gravity

Ever tried to make a pencil stand on your fingertip and succeeded? Or balanced rocks one over the other, carefully placing them so that your rock-tower does not collapse? These are the perfect examples of instances where the centre of gravity comes into play.

The centre of gravity of any object is an imaginary centre point where the body’s total weight is thought to be concentrated. It is used to calculate the behaviour of a body in motion when acted on by gravity. 

There is a difference between the centre of gravity and the centre of mass. The centre of gravity is determined by the weight of an object, which is mass affected by gravity. On the other hand, the centre of mass is determined only by the mass of that object, regardless of gravity.

Properties of Centre of Gravity

• Most uniform objects have their centre of gravity at their geometric centre.
• In some objects, the centre of gravity can also be located at a distance from the object’s geometric centre.
• In hollow or irregularly shaped objects, the centre of gravity is often located outside the physical body. Examples include chairs and rings.
• Only in a uniform gravitational field, where g (gravitational force) is constant, the centre of gravity is the same as the centre of mass.
• But for many objects, g varies. In such cases, the centre of gravity will move closer to a region where the object is in a stronger field than the uniform gravitational field.

Centre of Gravity’s Importance

The centre of gravity plays an important factor in the contemporary world of engineering and physics. Its primary function is to simplify calculations. This is because many physical and engineering calculations would become impossible to solve without defining the centre of gravity.

The importance of the centre of gravity rules can be felt in the automobile, space engineering, and other such scientific fields related to motion and balance. The International Space Station uses the centre of gravity to maintain attitude control up in space. In the design of cars, the centre of gravity helps prevent the toppling over of the vehicle easily. It also comes into play in gymnastics, sports, and everyday life.

How to find out the centre of gravity?

The centre of gravity can be easily found through a simple, practical experiment. If an object is supported on a point, and it stays there without toppling over, the point at which the object is balanced is its centre of gravity. In this case, the total gravitational torque about this particular point is zero, which helps it balance and also helps us determine the object’s centre of gravity.

The centre of gravity of the Moon

There are three centres that come into play when we talk about the centre of gravity of the Moon. The geometric centre, the centre of mass, and the centre of gravity. For the Moon, the geometric centre and the centre of mass are very close to each other. However, since the Moon is affected by the gravitational pull of the Earth, its g (gravitational force) is displaced. Therefore, the centre of gravity of the Moon, although within the Moon, is slightly displaced towards Earth. This is an important fact to remember to answer centre of gravity questions in your exam.

Centre of Gravity of different objects

Conclusion

From everyday acts of walking and balancing ourselves to the lengthy calculations that go into engineering and astrophysics, the centre of gravity plays an important role in everything. It is crucial to make a note of the properties of the centre of gravity. Finally, as you prepare for your exam, make sure to go through the frequently asked questions on the centre of gravity.