MECHANICS. 139 



the axis, would communicate to the bodies thus 

 collected the same angular velocity that it would 

 have communicated to the system in its first con- 

 dition. 



The point thus found is called the Centre of Gyra- 

 tion. 



Its distance from the axis of rotation is 



A+B+C+D 



ATWOOD OTi Rectilinear and Rotatory Motion, p. 



As every body may be considered as a system of phy- 

 sical points, it is evident that the preceding propo- 

 sitions are of general application. We shall give 

 examples in the cases of the cylinder and the 

 sphere. 



219. Let ADBE (fig. 15.) be a cylinder move- 

 able about an axis passing through C its centre ; let 

 the radius of the cylinder be given = r, and also 

 its weight = W ; and let another given weight F 

 hang by a cord BF, wound round the cylinder. 

 Required, the force accelerating the point B, and 

 the velocity which B will acquire in the first se- 

 cond of its iwotion. 



The 



