# Physics- center of mass problem ?

J.live

## Homework Statement

The coordinates of the center of mass for the extended object shown in the figure are (L/4, −L/5). What are the coordinates of m1? (Assume m1 = 4 kg, m2 = 2 kg, and m3 = 3 kg. Use any variable or symbol stated above as necessary.)

Here is the diagram : http://tinypic.com/view.php?pic=33da26e&s=7[

Can someone check my work?

4(x,y) + 3(-L/4,-3L/10) + 2(-3L/4,-L/4) = 0

-( 4x,4y) +(-3L/4,9L/10) + (-3L/2,-L/2) = 0

-4x - 3L/4 - 3L/2 = 0

-4y + 9L/10 - L/2 = 0

-4x = 9L/4

-4y = 4L/10

x = -9L/16

y = -L/10

Thanks.

J.live
Help :/?

Homework Helper
Gold Member
What axis have you chosen for calculating the moments of the masses? For the c.m. about the x axis, it's m1y1 + m2y2 + m3y3 = (m1 + m2 +m3) Y_c.m. , where the y1, y2, anmd y3 terms are the respective distances from the x axis, and Y_c.m. is given as -L/5.

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