Center of gravity of a person

[xlaserx7]

Homework Statement

a person is standing on a level floor. His head , upper torso , arm , and hand together weigh 438N and have a center of gravity that is 1.28 m above the floor. His upper legs weigh 144N and have a center of gravity that is .760 m above the floor. Finally, his legs and feet together weigh 87N and have a center of gravity that is .250 m above the floor. Relative to the floor, find the location of the center of gravity for his entire body

Homework Equations

x of cg = W(lever arm) of 1 + W(lever arm) of 2 / W of 1 +W of 2

The Attempt at a Solution

I don't know how to start. But i need to find the lever arm of each one? so 1.28 m = 438N (lever arm) / W?

 

[Doc Al]

Homework Equations

x of cg = W(lever arm) of 1 + W(lever arm) of 2 / W of 1 +W of 2

Here's what you want:
$$x_{cg} = \frac{W_1x_1 + W_2x_2 + W_3x_3}{W_{total}}$$

Read more about center of gravity (or center of mass) here: http://hyperphysics.phy-astr.gsu.edu/Hbase/cm.html"

 

[xlaserx7]

so do i use the center of gravity for each one as the lever arm?

 

[Doc Al]

You are treating the body as having three parts. Each part has its own weight and center of gravity. To find the overall center of gravity, you can treat each part as being a point mass located at its center of gravity.