The Student Room Group
Uni students - Complete our survey >>
Uni students - Complete our survey >>
Uni students - Complete our survey >>

Help me with these three things..

The centre of gravity of an object:

I know its a simplification of reality, but which is abetter definition:

1. A point where all the mass of the object can be thought to act

or

2. The average location of the weight of an object.

Personally I prefer two because in a regular object which is not uniformly dense, it will not be the geometric centre? idk im abit confused as to this, and do you think I could add some info to these two points? id also appreciate if you gave your own definitons

My second question was that can be the centre of gravity of an object all by itself, being acted upon by a force not through the said centre, be thought to be a pivot through which the moment can be calculated? i was just wondering because when an object is not acted upon through its centre of gravity, it is supposed (my assumption) ​to rotate?

third question is, how do I get better at physics, id appreciate any tips apart from doing as many questions as I can, thats probably a given, but how do I make the most of my time spent on it?
Reply 1
Avatar for pipyat
pipyat
1
Hi there. I would define the centre of gravity as the imaginary point on an object that the force of gravity is though to act. I can't really answer the second question because I am not familiar with moments. For the thirds question I'd say apart from past papers (because exam boards like to be tricky and l confusing) try and read further on the subject. It really helps if you accumulate wider knowledge. When you learn or revise a topic make notes describing it as simply as possible to yourself to really understand the laws and concepts. Then you can play around with them and apply them to different situations. Physics is a good balance between science and maths so try to maximise your inner scientist and inner mathematician by again reading further, practising a lot and getting a feel for concepts by revisiting them simply and arriving at your own conclusions. Best of luck.
1. Is centre of mass
2. is centre of gravity

2 is the single point where "gravity" appears to act on the body.

They are not the same thing but will correspond to the same place if the object is in a uniform gravitational field.

In all questions at A level you will have a uniform field and it doesn't matter in the final reckoning, whether you call it centre of mass or centre or gravity. Centre of gravity is the one where the weight acts, for example, in questions such as you mention, on moments, A body rotates if the applied force is not through its centre of mass. If you think about this, the statement would be true in space where you were not in the region of a gravitational field. So centre of gravity would be irrelevant.
(edited 9 years ago)

Quick Reply

Related discussions

Latest

Trending

Trending

Articles for you