Physics 101- Introduction to Mechanics
March 22- Rotational Dynamics

Kinematics

There is no new physics here- we're still talking about constant acceleration, forces, and conservation of energy.  We will simply be using new terminology to describe the circular motion.  We just will be using a different kind of coordinate system.

• Typically we try to use radians whenever discussing circular motion.
• Radians are unitless, so often will see speeds listed as sec-1.
The relationship between rotational variables is just like the linear ones.

How would you solve this-
A car has a constant acceleration of 0.35 m/s2.  If it starts from rest, how far does the car travel in 18 sec?  What is the car's speed at 18 sec?

No problem, right?  Okay, now try this one:

A wheel has a constant angular acceleration a= 0.35 rad/ sec2.  It starts from rest with an arbitrary reference line horizontal, at angular position qo=0.  What is the angular displacement of the reference line (and hence the wheel) at t= 18 sec?  What is the wheel's angular velocity at t= 18sec?

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 Jeff Phillips phillips@lmu.edu Loyola Marymount University Spring 2002