# Homework Help: Center of Mass question

1. Nov 3, 2009

### Dr_bug

1. The problem statement, all variables and given/known data
Discuss when you can and can’t “pretend all the mass of an object is concentrated at the center of mass”.

2. Relevant equations

3. The attempt at a solution
So I don't really understand what this is supposed to mean. I know that you utilize center of mass when trying to describe the motion of an extended object where different parts of the object is moving with different speeds. But so far i haven't come across anything you really couldn't use this... and explosion problem maybe... i don't really know and would appreciate some input thanks

2. Nov 3, 2009

### rock.freak667

Maybe when explaining the motion of large objects, like aeroplanes or human movements

3. Nov 3, 2009

### Dr_bug

well you actually do use center of mass to describe human movements because thats an example that my text book uses...

4. Nov 4, 2009

### rock.freak667

Well I meant like in testing car crashes, I don't think they consider the entire body as one point mass.

OR analysis of the forces on an aeroplane.

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