Uni Project Help: Weight & Force Calculations

[deborah_88]

1. HI, please help! this is for a project I'm doing at uni and not sure where to start! Ok so I've got a circular plate with 16 equally spaced holes around the outside. In 15 of these holes are small bottles which are screwed in. (see attached pic). The plate dimensions are: 340mm diameter; 41mm diameter holes and 20mm thickness. The plate weighs 2kg and the bottles weigh 25g. Basically, the plate (and attached bottles) will be rotated via an axle attached to the centre of the plate. This axle will be attached to gearing and a torsion spring which, when loaded, will turn the plate. What I need to do is come calculations on this...what I'm not sure about is how to relate the weight of the plat and bottles acting down, and the force needed to turn it?2. I think I'll need to look at friction and forces but not sure how! All fiction examples seem to use a slope with a box on it, but how do I manipulate this into what my application is?! Also, will i need to find the centre of gravity as one bottle is "missing" so it won't be the centre of the plate anymore??3. PLEASE HELP! THANK YOU!

 

[deborah_88]

sorry here's the attachment..!

 

[MisterX]

For the Center of Gravity:
If you want to do a theoretical calculation, you can think of it like a system of point masses. Use polar coordinates, and maybe don't bother to find the axial (up-down direction) component of the center of mass.The center of mass of the plate is at it's center, so it will have no contribution to the sum of the numerator because |r| is zero, but it will change the 1/(total mass) part. ris the position vector