Projectile and Circular Motions
2D Motion
Two special types of motion in 2D
Projectile motion (today)
Uniform circular motion (tomorrow)
Key to remember that , , directions are independent of
each other
Projectile Motion
In this course, projectile motion
Newtons First Law
Law of Inertia
Ancient Greeks:
The preferred state of all objects is to be at rest
=0
=0
Law of Inertia
Galileo:
In the absence of forces, the velocity stays the same
(This property is called inertia)
=0
=0
Law of Inertia
Inertia is the
Sig. Figs. and Vectors
Significant Figures
True or False:
2 m = 2.00 m = 2.0000 m?
Math student says True
Science student (should) say False
Why the difference?
In science, we only write down digits corresponding to
the precision of our measuring tools
Si
Motion in 2D and 3D
Definitions
Position and Displacement
= + +
= 2 1 = 2 1 + 2 1 + 2 1
Definitions
Velocity
=
= lim
=
+
+
= + +
Were doing the same stuff as last week, but now in the
y and z coordinates as well
Velocity in 2D
Magnitude
=
2 + 2
Units
Why Units?
First, its required.
(This is physics, not math!)
Second, always asking how far/much/long need a way to
standardize measurements
All physical quantities have a unit, however a small
number of base units allow us to express all our
measure
PHY 211 Homework #1
Due by 1am on Tuesday, September 6th
Submit your answers for the problems below on the course moodle page. By submitting this
assignment, you attest that youve done your own work.
Math Reviews
1. What are the solutions to the equation
PHY 211 Homework #3
Due by 1am on Tuesday, September 20th
Submit your answers for the problems below on the course moodle page. By submitting this
assignment, you attest that youve done your own work.
Displacement, Velocity, Acceleration
1. Chapter 3, Pro
Physics 211
Physics for Science and Engineering I
Prof. Myers
My Story
Originally from Indiana
Physics and Math major at Indiana University
Ph.D. in Physics from the University of Illinois
Postdoctoral fellowships at Duke University and
Jefferson Laborato
Kinematics I
Displacement
Velocity
Speed
Definitions and Relations
Position, Displacement, and Distance
Simplifications
1. Assume that we can describe all objects as point
particles (i.e. ignore size and shape)
2. Restrict motion to one dimension (i.e.
PHY 211 Homework #2
Due by 1am on Tuesday, September 13th
Submit your answers for the problems below on the course moodle page. By submitting this
assignment, you attest that youve done your own work.
Displacement and Velocity
1. Chapter 2, Problem 15(a)
Newtons Second Law
Law of Inertia
The first law covers the case when = 0
What if the force is not zero?
=?
0
Observation
Acceleration increases if net force increases and/or
the mass decreases
Newtons Second Law
=
= 1 + 2 +
Note that the acceleration d
Kinematics II
Motion with Constant Acceleration
The Big 5 Equations
Concept
Last time, we found velocity and acceleration from
position. But how can we find position from velocity
and/or acceleration
Average velocity
=
=
Instantaneous velocity
Aver