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M2 Centre of Mass (Simple understanding query)




Can someone confirm how I can take moments here without masses?

I used a c.o.m equation, divided by total lengths and got the answer in the marks scheme but they divide by 3 in there and I'm not sure why the 3 works - is it because there are 3 masses of equal weight so the weights all cancel out?​
Original post by Ki Yung Na



Can someone confirm how I can take moments here without masses?

I used a c.o.m equation, divided by total lengths and got the answer in the marks scheme but they divide by 3 in there and I'm not sure why the 3 works - is it because there are 3 masses of equal weight so the weights all cancel out?​


You assume a certain mass per unit length.
Each part of the framne can be repalced by a mass placed at its mid-point hence 3 masses.
Original post by Ki Yung Na



Can someone confirm how I can take moments here without masses?

I used a c.o.m equation, divided by total lengths and got the answer in the marks scheme but they divide by 3 in there and I'm not sure why the 3 works - is it because there are 3 masses of equal weight so the weights all cancel out?​


The centre of mass equation is when you taking moments about a given point in the X and Y direction.
Original post by brianeverit
You assume a certain mass per unit length.
Each part of the framne can be repalced by a mass placed at its mid-point hence 3 masses.


That's a good explanation for my fluffy description. Thanks for the clarification!

Original post by Jai Sandhu
The centre of mass equation is when you taking moments about a given point in the X and Y direction.


That isn't quite what I was asking about.
(edited 8 years ago)
Original post by Ki Yung Na
That isn't quite what I was asking about.


Was just saying as you were referring to it as the centre of mass equation which is isnt really.
Original post by Jai Sandhu
Was just saying as you were referring to it as the centre of mass equation which is isnt really.


"A com equation" not "the equation" - in other words; I didn't say that it wasn't taking moments but rather I was asking how it was.

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Original post by Ki Yung Na

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Probably, sorry for the confusion.

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