Download Study Notes for Test 3

PHYS 111-6
Notes for Test 3
Chapter 4 Forces and Newton’s Laws of Motion
Concept Summary is on p. 123.
You should be familiar with the concepts of force and mass. In particular, you should know the distinction
between mass and weight.
You should know that force is a vector and mass is a scalar.
You should know the units associated with Newton’s second law, F  ma (see Table 4.1).
You should know how to use Newton’s second law of motion to find any one of its three variables ( F , m or a )
given the other two.
You should know how to use Newton’s second law of motion in two dimensions by using components. (See
your lecture notes and Example 3 in Chapter 4 of your text.)
You should be familiar with Newton’s third law of motion and how to identify an action-reaction pair of forces.
You should know how to calculate the accelerations produced by action and reaction forces. (See Example 4.)
You should know how to solve problems dealing with both equilibrium and nonequilibrium applications of
Newton’s second law of motion. (See Examples 12 and 14.)
You should be familiar with the theory of friction discussed in class. You should know how to use equations
that relate the force of friction to the normal force. You should be familiar with friction on an inclined plane and
the conditions that relate the angle of the incline to the appropriate coefficient of friction.
You should know how to use the equation w  mg to find the weight w of a mass m at a location where the
acceleration due to gravity is g.
You should know how to calculate the apparent weight of an object in an elevator (or other environment such as
a rocket ship) that is accelerating upward or downward.
Chapter 5 Dynamics of Uniform Circular Motion
Concept Summary is on p. 154.
You should know that the term “uniform circular motion” means motion in a circle with constant speed v.
You should know that uniform circular motion is an example of periodic motion, that is, motion that repeats
itself with characteristic cycles. The time for one cycle is called the period T of the motion.
You should know that the speed v of the motion is related to the period T by v 
2r
, where r is the radius of
T
the circular path.
You should know that an object in circular motion has an acceleration directed towards the center of the circular
path. This acceleration is known as centripetal acceleration and is given by ac 
v2
.
r
By Newton’s first law of motion an unbalanced force must cause an object of mass m move in a circular path.
By Newton’s second law of motion this force must be directed toward the center of the path of motion and
mv 2
given by Fc 
. This force is called centripetal force. A centripetal force can be supplied by any kind of a
r
force: a tension, a normal force, a gravitational force, a frictional force are common examples. (See Example 5
in Chapter 5 of your text.)
You should know how to use Equation (5.4) to find the proper banking angle of a circular curve. (See Example
8.)
You should know that for a satellite in orbit the force of gravity provides the centripetal force. You should know
how to use Equations (5.5) and (5.6) to find the speed and period, respectively, of a satellite in a circular orbit.
(See Examples 9 and 10.)
You should know that apparent weightlessness occurs for objects in free fall. You should know how artificial
gravity can be created in a rotating space station. (See Examples 13 and 14.)