180

Summary

Selected Vocabulary

uniform circular motion.........circular motion in which the magnitude of the velocity vector remains

constant

nonuniform circular motion...circular motion in which the magnitude of the velocity vector changes

radial......................................parallel to the radius of a circle; the in-out direction

tangential...............................tangent to the circle, perpendicular to the radial direction

Notation

a

r...................................................................

radial acceleration; the component of the acceleration vector along the in-

out direction

a

t....................................................................

tangential acceleration; the component of the acceleration vector tangent

to the circle

Summary

If an object is to have circular motion, a force must be exerted on it toward the center of the circle. There is

no outward force on the object; the illusion of an outward force comes from our experiences in which our point

of view was rotating, so that we were viewing things in a noninertial frame.

An object undergoing uniform circular motion has an inward acceleration vector of magnitude

|a| =

v

2

r

.

In nonuniform circular motion, the radial and tangential components of the acceleration vector are

a

r

= |v|

2

/r

a

t

= slope of the graph of |v| versus t .

Chapter 9Circular Motion