# What is the center of mass of the remaining part of the sphere ?

1. Oct 3, 2004

### mlee

Please who can solve this for me....
Many thanx

A solid sphere has a mass of 25 kg and a radius of 30cm. The center of the sphere is placed at the origin,x=0,y=0,z=0. The sphere is cut and the part of the sphere above z=7cm is removed.
What is the center of mass of the remaining part of the sphere ?

PLease help me, i am very confused...
Thank you very much

2. Oct 3, 2004

### arildno

Welcome to PF!
How are you used to calculating the center of mass of systems consisting of several objects?

3. Oct 3, 2004

### CollectiveRocker

Use the center of mass equation. (((x)1*m(1)) + (x(2)*m(2)) + (x(3)*m(3))) / (m(1) + m(2) + m(3))

4. Oct 3, 2004

### mlee

there's a given hint: by symmetrie u can see that the center of mass lies along the z-axis. slice the sphere up in discs of thickness dz and integrate over z to find the center of mass

5. Oct 3, 2004

### arildno

Use that hint!

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