9781118230725.pdf

9-1 CENTER OF MASS 219

A

The com of the composite

plate is the same as the

com of the two pieces.

PlateP

2 R

R

y

x

y

y

x

comP

comC

comS

DiskS

Composite plate

C = S + P

(a)

(b)

(c)

(d) x

comS comCcomP

Disk particle Plate particle

Assume the plate's

mass is concentrated

as a particle at the

plate's center of mass.

Here too, assume the

mass is concentrated

as a particle at the

center of mass.

Here too.

Here are those

three particles.

Figure 9-4(a) Plate Pis a metal plate of radius 2R, with a circular hole of radius R. The center of mass of Pis at point comP.(b) Disk S.
(c) Disk Shas been put back into place to form a composite plate C.The center of mass comSof disk Sand the center of mass comC
of plate Care shown. (d) The center of mass comSPof the combination of SandPcoincides with comC, which is at x0.