Chapter 8: Rotational Motion•Pure rotational motion means the circular movement of a ‘rigid body’ where all points have the same angular motion…this motion spins about an axis of rotation.•We will use angular quantities of angular velocity and angular acceleration that have analogical relationship to their linear counter-part.

Angular Quantities

• One radian is defined as the angle subtended by an arc whose length is equal to the radius.

• 360o = 2p radian or 1 radian = 57.3o • Angular velocity is the change in angular

displacement per unit of time… w= /Dq Dt• Instantaneous angular velocity is described as

a limit of, as Dt 0 w= /Dq Dt.

Angular Quantities (cont’d)

• Angular acceleration a= Dw/Dt.• Instantaneous angular acceleration is

described as a limit of, as Dt 0 a= /Dw Dt.• vt = rw (Vt = tangential velocity)

• ac = vt2 /r = (wr)2 /r= w2r

• at =ra

• ac = ar = centripetal acceleration or radial component of acceleration.

Homework

• Page 234 pr#1-10