[Physics Class Notes] on Centre of Gravity Pdf for Exam

In Physics the topic centre of gravity is a point which is imaginary in a body of matter whereas for the convenience it uses in certain calculations. The weight of the body may be thought to be concentrated at a point. This whole concept is sometimes useful in designing of static structures that is buildings and bridges or we can say in predicting the behaviour of a bodies which are moving when it is acted on by gravity.

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When taking a drum and it is  stood on end, its centre of gravity that is denoted by CG is firmly supported and the drum is in stable equilibrium which is denoted as A. If the drum is slightly tilted to either side, suppose B, the gravity’s pull on this centre creates a torque or we can say a turning force which is around the new point of support and it again pulls the drum back to the stable position. A drum can balance on its rim suppose C is in unstable equilibrium. Even a very tiny displacement denoted in D will create a torque that will turn the drum from the position which is unstable.

The two of them do not always coincide. Taking an example of the moon the Moon’s centre of mass is very close to its geometric centre  that is it is not exactly  because the Moon is not a perfect or a uniform sphere but rather its centre of gravity is slightly displaced toward that of planet Earth because of the stronger gravitational force on the Moon’s near side of Earth.

In cases such as bodies which are hollow or irregularly shaped objects, in them the centre of gravity or we can say the centre of mass may occur in space at a point which is external to the physical material that is in the centre of a tennis ball or between the legs of a chair.

Center of Gravity and Balance

We have nearly heard someone saying that one of the advantages of being stocky and short is that you’re very less to get knocked over it. We can say that we might have even mentioned earlier that it’s because the stocky and short person has a lower center of gravity. But still in many objects we can say that it’s a fixed location.

A quick experiment is we need the following:

• A 2 pencil set.

• A edge which is fine like a ruler or a credit card.

• A marker which is permanent.

• A ruler if we don’t have one we may be able to eyeball it.

First Step: an Attempt which is done to balance the pencil on the edge which we have selected.

The pencil which balances them may take some trial and error method to work. The point at which the balancing pencil may not be where we first thought it to be. Once it begins to tip and that too in one direction, which moves the pencil slowly back slowly in the direction which is in the opposite direction until it will stay there on its own.

Second Step: Once we see the pencil is balanced in a direction the mark the location of the balancing point with a marker which is a permanent marker.

Third Step: This step is done basically to measure the distance which is between the ends of the pencil and this is the balancing point which we  have marked. Can we see that the two lengths are equal? On our pencil the length which is from the eraser to the balancing point was actually 1.25 inches that is even less than the length from the tip of the pencil to the point which is balancing.

In the experiment which we are performing the point of balancing was the another word for the center of gravity of that pencil. We can notice that there are two parts which would be equal in weight. They are not equal in length however. As we may have found out that the piece of metal that houses the eraser contributes more to the weight of pencil weight. so the CG that is the center of gravity is closer to another side of the pencil.

The CG or even we can call the center of gravity is a very important concept in determining the stability of a structure. It’s the reason why a good homeowner will keep the top branches of his trimmed trees. It’s also the reason why a pick-up truck might not be the best vehicle choice for a first time driver.

Stability is maximized in objects with a lower center of gravity and a wide base. As it is the heavier the top and taller the more which is likely to tip over when it is tilted by a force. It clearly denotes that the bus which is driving on different two grades the second one is even more steep enough to cause the center of gravity or CG which is to fall outside of the base of the vehicle which can cause it to topple.