# Center of mass?

1. Jul 22, 2006

### uwmphysics

Can someone explain how center of mass changes? We haven't actually learned about the center of mass, so I dont know how to even approach this homework question.

ok so here's the question:

If you stand with your back against a wall, you find you can not bend over to pick something up, because your
a. center of mass moves forward beyond your toes.
b. vertical and horizontal motions are independent.
c. center of mass is located at a fixed position in your body.
d. center of mass hits the wall.

thank you

2. Jul 22, 2006

### arildno

The position of the center of mass can change if the shape of the object changes.
What does that tell you?

3. Jul 22, 2006

### uwmphysics

well if the center of mass changes as your shape changes, then the answer cant be that the center of mass is located at a fixed point in your body. Is there a way to find out where the center of mass is in an object?

4. Jul 22, 2006

### arildno

Well, think of it in the following manner:
I see that you've not formally started your study of centre of mass, so I'll give you an intuitive understanding:

Suppose you managed to stand with your legs straight up along the wall, and your upper body was bent 90 degrees out in the horizontal from the wall.

Question:
Would most of your mass lie directly above your legs, or would it sort of "float" some distance away from the wall&your legs?