Many people assume that the terms “centre of mass” and “centre of gravity” are synonymous, but this is not the case.
Centre of mass is the point at which the distribution of mass is equal in all directions, and does not depend on gravitational field. Centre of gravity is the point at which the distribution of weight is equal in all directions, and does depend on gravitational field.
A toy bird balances when a pivot is placed at its centre of gravity.
The centre of mass and the centre of gravity of an object are in the same position if the gravitational field in which the object exists is uniform. In most cases this is true to a very good approximation: even at the top of Mount Everest (8848 metres) the gravitational field strength is still 99.6% of its standard value. You are unlikely ever to experience a difference between centre of mass and centre of gravity, as the gravitational field in which you find yourself is extremely uniform.
But if the gravitational field strength were greater towards your feet and weaker towards your head, then your centre of gravity would be below your centre of mass, perhaps somewhere around your knees. If the gravitational field strength were greater towards your head, and weaker towards your feet, then your centre of gravity would be above your centre of mass, perhaps somewhere around your shoulders.
The object on the left, in a uniform gravitational field, has overlapping centres of gravity and mass. For the object on the right, in which the gravitational field is stronger towards its base, the centre of gravity is below the centre of mass. Approaching a black hole the gradient of the gravitational field would be infinitely “steep”, leading to an incredible difference in gravitational field and death by spaghettification for anyone falling into a black hole.
The toy bird is not balancing at its centre of gravity, the pivot point is in line (vertically, in the direction of gravitational force) with the models centre of gravity which could be above, below or at the pivot point. at least that was what I was taught. Could be wrong I guess.
Ps – most interesting info on your site, good stuff.
Good exlpanation but need simple words.
The toy bird is balancing with its centre of gravity below its pivot. That is why equilibrium is restored after it wobbles. It is in a state of stable equilibrium. If the centre of gravity were at the pivot, it would be in a state of neutral equilibrium and it will remain in that new position if if the toy bird is left at rest. If the centre of gravity were above the pivot, it would be in a state of unstable equilibrium and the toy bird will rotate until it achieves stable equilibrium.
I am aman raj ok!
very helpfull & interesting
Good briefing.Thanks.
the centre of mass and centre of gravity of toy bird coincide at that point where it is pivoted.
Clot answer
Helpfull for me
Briefly answered
Very helpful thank u so much for wonder ful explanation
nice i like it very help full sir.
Best explanation sir
What about ice bergs COM AND COG
That is a really interesting point. That needs some thought.
It is very useful and I have understood briefly
It always amazes me that people don’t understand the difference between COM and COG. As someone who works in game development, the separation of the two terms is critical when it comes to making your physics engine work properly…. excellent post.
Sir if COG is above or below from the pivot than how Toy bird will rotate???
Because in this case moment arm will zero and the torque will also zero as
Torque=moment arm ? force
As
Moment arm=0
Force=weight
Then
Torque= 0 ? weight
Torque=0
Yes, the bird will not rotate. It will just stay where it is.
Best explination sir
Good explanation
Nice explanation
very good
Very useful
Of an object is cut into two pieces exactly at its centre of gravity, whether both pieces weigh equal?
If the object is uniform, yes.
Why does the center of gravity shifts?
Because the gravitational field is not uniform.