Hi all
I've been searching and searching and cannot find a way to determine the 
centre of gravity of a cylinder of height h and radius r

Any one have some pointers?
TIA

sheri

-- 
Life may not be the party we hoped for, but whilst we are here we might as 
well dance

~Bitzchick~ wrote:
> Hi all
> I've been searching and searching and cannot find a way to determine
> *where*the centre of gravity of a cylinder of height h and radius r is 
> from the end
> Any one have some pointers?
> TIA
>
I have assumed it to be at h/2  from ends and r from the sides but am 
getting thrown as it's a 2-d shape

sheri

"~Bitzchick~"  wrote in message 
news:XINQi.31613$c_1.24284@text.news.blueyonder.co.uk...
> ~Bitzchick~ wrote:
>> Hi all
>> I've been searching and searching and cannot find a way to determine
>> *where*the centre of gravity of a cylinder of height h and radius r is 
>> from the end
>> Any one have some pointers?
>> TIA
>>
> I have assumed it to be at h/2  from ends and r from the sides but am 
> getting thrown as it's a 2-d shape
>
> sheri
>

Can you expand on why you say it's a 2-d shape...?  I always thought a 
cylinder was 3-d by definition (assuming neither r nor h are zero)


-- 
Martin

Martin wrote:
> "~Bitzchick~"  wrote in
> message news:XINQi.31613$c_1.24284@text.news.blueyonder.co.uk...
>> ~Bitzchick~ wrote:
>>> Hi all
>>> I've been searching and searching and cannot find a way to determine
>>> *where*the centre of gravity of a cylinder of height h and radius r
>>> is from the end
>>> Any one have some pointers?
>>> TIA
>>>
>> I have assumed it to be at h/2  from ends and r from the sides but am
>> getting thrown as it's a 2-d shape
>>
>> sheri
>>
>
> Can you expand on why you say it's a 2-d shape...?  I always thought a
> cylinder was 3-d by definition (assuming neither r nor h are zero)

Sorry I meant a 3-d shape. As it has curvature I wasn't sure that the C of G 
of a cylinder would be in the same place as a cuboid of side length l and 
cross section h^2

Thinking about it the C of G of a cylinder is of uniform cross secion so the 
C of G must be in the centre of half the length and half the diameter

sheri

~Bitzchick~ wrote:

> Martin wrote:
> 
>>"~Bitzchick~"  wrote in
>>message news:XINQi.31613$c_1.24284@text.news.blueyonder.co.uk...
>>
>>>~Bitzchick~ wrote:
>>>
>>>>Hi all
>>>>I've been searching and searching and cannot find a way to determine
>>>>*where*the centre of gravity of a cylinder of height h and radius r
>>>>is from the end
>>>>Any one have some pointers?
>>>>TIA
>>>>
>>>
>>>I have assumed it to be at h/2  from ends and r from the sides but am
>>>getting thrown as it's a 2-d shape
>>>
>>>sheri
>>>
>>
>>Can you expand on why you say it's a 2-d shape...?  I always thought a
>>cylinder was 3-d by definition (assuming neither r nor h are zero)
> 
> 
> Sorry I meant a 3-d shape. As it has curvature I wasn't sure that the C of G 
> of a cylinder would be in the same place as a cuboid of side length l and 
> cross section h^2
> 
> Thinking about it the C of G of a cylinder is of uniform cross secion so the 
> C of G must be in the centre of half the length and half the diameter
> 
> sheri 
> 
> 

The center of gravity is a point in space.  Essentially the body as a 
whole will operate as though the mass were concentrated at that point. 
Assuming that the cylinder is uniform it should be at the geometric 
center of the figure.  It is often described as the center of mass so 
that possible differences in gravitational field do not have an effect.

If the figure is not uniform you will need to integrate the density 
function to find the center.

http://www.grc.nasa.gov/WWW/K-12/airplane/cg.html

Frank F. Matthews wrote:
> ~Bitzchick~ wrote:

>> Sorry I meant a 3-d shape. As it has curvature I wasn't sure that
>> the C of G of a cylinder would be in the same place as a cuboid of
>> side length l and cross section h^2
>>
>> Thinking about it the C of G of a cylinder is of uniform cross
>> secion so the C of G must be in the centre of half the length and
>> half the diameter

> The center of gravity is a point in space.  Essentially the body as a
> whole will operate as though the mass were concentrated at that point.
> Assuming that the cylinder is uniform it should be at the geometric
> center of the figure.  It is often described as the center of mass so
> that possible differences in gravitational field do not have an
> effect.
> If the figure is not uniform you will need to integrate the density
> function to find the center.
>
> http://www.grc.nasa.gov/WWW/K-12/airplane/cg.html

Thank you very much, Frank, for that information. Yes,  I had to integrate 
to find the centre of mass of a cone, so I understand what you mean

Thanks again

sheri