roulette wheel. All of these are objects whose motion is described by the time
dependence of a single variable, the angle of rotation. We shall study the angular
equivalent of uniformly accelerated motion for some rotating objects.This
lesson also begins the study of rotational dynamics by introducing the dynamic
quantities torque and angular momentum for a point mass moving in a plane.
A diver, in making several turns in the air, grabs his knees to achieve a
high rate of rotation, and a skater does much the same thing when she goes into
a spin with arms and legs extended but brings them in close to her body for the
extremely rapid part of this motion. In this lesson, we will consider the physics
describing these motions, and those of other rotational systems, such as the
starting or stopping of a record turntable (or a washing-machine tub), or the
unwinding of the winch cord as a bucket is dropped into a well. We will begin
our study by expanding on a topic that was only alluded to in the last lesson:
moment of inertia, the analog of mass in the equations of rotational dynamics.
PREREQUISITE: Describing the motion of a body in uniform circular motion.
Defining the center of mass for a system of particles or extended body.

Week of March 2, 1998
Lesson 8Equilibrium of Rigid Bodies
Keywords: statics, equilibrium, translational equilibrium, rotational equilibrium,
OBJECTIVE:
* Define the following terms and describe the application of each to a physical object
or system: first condition of equilibrium (translational); second condition of
equilibrium (rotational); center of gravity.
Comments: Most of the objects that one sees are in a state of equilibrium, that
is, at rest or in a state of uniform motion. Many man-made structures are
designed to achieve and sustain a state of equilibrium, and this, in turn, sets
requirements for the structural components (such as their sizes and shapes) that
can be used. This lesson will give you some practice in analyzing the forces that
result in equilibrium. From this analysis, if you are given the values of an
appropriate set of forces you can find the remaining ones. On the other hand, in
designing a stable system you can find the requirements for materials and
dimensions that will ensure equilibrium.
PREREQUISITE: Locating the center of mass of a uniform rigid body (Lesson 9)
Thursday of the Eighth Week - Second Hour Exam - March 5th - 80 points

Week of March 9, 1998
Lesson 9Gravitation
Keywords: gravity, law of universal gravitation, gravitational forces, gravitational
fields,
OBJECTIVE: Use Newton's law of universal gravitation to determine (a) the (vector)
gravitational force exerted by one object on another (b) the distance of a mass when
the force is known; and (c) the gravitational field of an object.
Comments: The members of the solar system - the sun, the moon, and the
planets - have held a strong fascination for mankind since prehistoric times. The
motions of these heavenly bodies were thought to have important specific