Physics 121
Mechanics
Course Overview
Dr. Mark C. Waterbury
Lectures by James L. Pazun
1
Models, Measurements and
Vectors
Goals for Chapter 1
•
To know standards and units and be able to do
unit conversions.
•
To express measurements and calculated
information with the correct number of
significant figures.
•
To be able to add vectors.
•
To be able to break down vectors into
x
and
y
components.
Measurement
•
Physics is an experimental science.
–
Observe phenomena in nature.
–
Make predictions.
•
Models
•
Hypothesis
•
Theories
•
Laws
Lectures by James L. Pazun
2
Motion Along a
Straight Line
Goals for Chapter 2
•
Become comfortable with displacement,
velocity, and acceleration.
•
Explore motions at constant acceleration.
•
Be able to graph and interpret graphs as they
describe motion.
•
Be able to reason proportionally.
•
Examine the special case of freely falling bodies.
•
Consider relative motion.
Motion
•
Motion is divided into two areas of study:
–
Kinematics
•
This will be our focus in chapter 2.
•
Kinematics describes the movement of the object.
–
Dynamics
•
Will come in Chapter 4 and after.
•
Dynamics answers the
“
Why is this object moving?
”
question.
Lectures by James L. Pazun
3
Motion in a Plane
Goals for Chapter 3
•
To study position, velocity, and acceleration
vectors.
•
To frame two

dimensional motion as it occurs in
the motion of projectiles.
•
To restrain two

dimensional motion to a circular
path and understand uniform circular motion.
•
To study the new concept of one motion frame
relative to another.
Velocity in a plane
•
Vectors in terms of Cartesian
x
and
y
coordinates may
now also be expressed in terms of displacement and
angle.
Lectures by James L. Pazun
4
Newton
’
s Laws of Motion
Goals for Chapter 4
•
To understand force
–
either directly or as the
net force
of multiple components.
•
To study and apply Newton
’
s First Law.
•
To study and apply the concept of mass and
acceleration as components of Newton
’
s
Second Law.
•
To differentiate between mass and weight.
•
To study and apply Newton
’
s Third Law.
•
To open a new presentation of problem data in
a free body diagram
.
Dynamics, a new frontier
•
Stated previously, the onset of physics separates
into two distinct parts:
–
statics and
–
dynamics.
•
So, if something is going to be dynamic, what
causes it to be so?
–
A force is the cause, it is either
•
pushing or
•
pulling.
Types of Force Illustrated I
–
Figure 4.1
Lectures by James L. Pazun
5
Applications of
Newton
’
s Laws
Goals for Chapter 5
•
To study conditions that establish equilibrium.
•
To study applications of Newton
’
s Laws as they
apply when the net force is not zero.
•
To consider contact forces and the effects of
friction.
•
To study elastic forces (such as spring force).
•
To consider forces as they subdivide in nature
(strong, electromagnetic, weak, and
gravitational).
Two dimensional equilibrium
–
Example 5.2
•
Both
x
and
y
forces must be considered separately.
•
Follow worked example 5.2 on page 130.
Lectures by James L. Pazun
6
Circular Motion and Gravitation
Goals for Chapter 6
•
To understand the dynamics of circular motion.
•
To study the unique application of circular
motion as it applies to Newton
’
s Law of
Gravitation.
•
To examine the idea of weight and relate it to
mass and Newton
’
s Law of Gravitation.
•
To study the motion of objects in orbit as a
special application of Newton
’
s Law of
Gravitation.
In section 3.4
•
We studied the kinematics of circular motion.
–
Centripetal Acceleration
–
Changing velocity vector
–
Uniform Circular Motion
•
We acquire new terminology.
–
Radian
–
Period
–
Frequency
Lectures by James L. Pazun
7
Work and Energy
Goals for Chapter 7
•
Overview energy.
•
Study work as defined in physics.
•
Relate work to kinetic energy.
•
Consider work done by a variable force.
•
Study potential energy.
•
Understand energy conservation.
•
Include time and the relationship of work to
power.
Introduction
•
In previous chapters we studied motion
–
Sometimes force and motion are not enough to solve a
problem.
–
We introduce
energy
as the next step.
An Overview of Energy
•
Energy is conserved.
•
Kinetic Energy describes motion and relates to the mass of
the object and it
’
s velocity squared.
•
(some) Energy
on earth originates from the sun.
•
Energy on earth is stored thermally and chemically.
•
Chemical energy is released by metabolism.
•
Energy is stored as potential energy in object height and mass
and also through elastic deformation.
•
Energy can be dissipated as heat and noise.
Lectures by James L. Pazun
8
Momentum
Goals for Chapter 8
•
To study momentum.
•
To understand conservation of momentum.
•
To study momentum changes during collisions.
•
To add time and study impulse.
•
To understand center of mass and how forces act
on the c.o.m.
•
To apply momentum to rocket propulsion.
Momentum is a vector quantity.
–
Figure 8.1
Momentum can cause injury ( a concussion)
This is a frame of reference problem just like a passenger in a car. When the brain and skull are
moving at the same velocity, there is no problem. If the skull changes abruptly the brain does
not, there is a possibility of an injury.
Lectures by James L. Pazun
9
Rotational Motion
Goals for Chapter 9
•
To study angular velocity and angular
acceleration.
•
To examine rotation with constant angular
acceleration.
•
To understand the relationship between linear
and angular quantities.
•
To determine the kinetic energy of rotation and
the moment of inertia.
•
To study rotation about a moving axis.
Rigid bodies can rotate around a fixed axis.
–
Figure 9.1
Lectures by James L. Pazun
10
Dynamics of Rotational
Motion
Goals for Chapter 10
•
To study torque.
•
To relate angular acceleration and torque.
•
To examine rotational work and include time to study
rotational power.
•
To understand angular momentum.
•
To examine the implications of angular momentum
conservation.
•
To study how torques add a new variable to
equilibrium.
•
To see the vector nature of angular quantities.
Definition of torque
–
Figure 10.1
•
Torque (
⤠i猠摥晩湥f 慳
瑨攠f潲c攠e灰li敤
浵汴m灬p敤 b礠瑨攠t潭敮o
慲洮†
•
The moment arm is the
perpendicular distance
from the point of force
application to the pivot
point.
•
=
F
l
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