center of mass

[mathstresser]

The mass mi is located on the point Pi. Find the moments Mx and My and the center of mass of the system.
m1=6, m2= 5, m3=10;
P1(1,5), P2(3,-2), P3(-2,-1)

I found that Mx= (6)(1)+(5)(3)+(10)(-2)=1 and My= (6)(5)+(5)(-2)+(10)(-1)=10

M=6+5+10=21

so the points are

x= 1/21 and y= 10/21 which is

(1/21,10/21)

But, the answer is

10; 1; (1/21,10/21)
How do they get the first two answers?

 

[Guest]

The 10 and the 1 are the 2 moments that you have calculated, the moment around the x axis and the moment around the y axis. The moment around the x axis is the y distances and visa versa.

 

[mathstresser]

Thanks... I was wondering about the moment thing, and the order.... but I get it now...

Thank you!