Transcript Introduction to Modern Physics PHYX 2710

Physics of Technology
PHYS 1800
Lecture 18
Introduction
Review for Test 2
Section 0
Lecture 1
Slide 1
INTRODUCTION TO Modern Physics PHYX 2710
Fall 2004
Physics of Technology—PHYS 1800
Spring 2009
Review
Lecture 17 Slide 1
PHYSICS OF TECHNOLOGY
Spring 2009 Assignment Sheet
Date
Day
Lecture
Chapter
Jan 5
M
Class Admin: Intro.Physics Phenomena
1
6
T
Problem solving and math
App. B, C
7
W
Units, Scalars, Vectors,
1
9
F*
Speed and Velocity
2
Jan 12
M
Acceleration
2
14
W
Free Falling Objects
3
16
F*
Projectile Motion
3
Jan 19
M
Martin Luther King
No Class
21
W
Newton’s Laws
4
23
F*
Mass and Weight
4
Jan 26
M
Motion with Friction
4
28
W
Review
1-4
1-4
29
Th
Test 1
30
F
Circular Motion
5
Feb 2
M
Planetary Motion and Gravity
5
4
W
Energy
6
6
F*
Harmonic Motion
6
Feb 9
M
Momentum
7
11
W
Impulse and Collisions
7
13Introduction
F*
Rotational
8
Section
0 Motion
Lecture 1 Slide 2
Feb 16
M
Presidents Day
No Class
17
Tu
Angular Momentum (Virtual Monday)
8
18
W
Review
5-8
19
5-8
H
Test 2
INTRODUCTION TO Modern Physics PHYX 2710
20
F*
Static Fluids, Pressure
9
Fall 2004
Feb 23
M
Flotation
9
25
W
Fluids in Motion
9
27
F*
Temperature and Heat
10
Mar 2
M
First Law of Thermodynamics
10
Physics of Technology—PHYS 1800
4
W Spring 2009Heat flow and Greenhouse Effect Review 10
*Homework
Handout
6
F*
Climate Change
-
Homework Due
-
1
2
3
4
5
-
6
Lecture 17 Slide 2
7
Physics of Technology
PHYS 1800
Lecture 8
Circular Motion
Gravitational Forces
Conservation of Energy
Conservation of Momentum
Conservation of Angular Momentum
Introduction
Section 0
Lecture 1
Slide 3
Introduction and Review
INTRODUCTION TO Modern Physics PHYX 2710
Fall 2004
Physics of Technology—PHYS 1800
Spring 2009
Review
Lecture 17 Slide 3
Notes on Test
1. Covers Chapters 5-8 (Chapter 8 only qualitatively)
2. ~8 short answer problems or questions (5 point
each)
3. 3 Numerical problems based heavily on the
material from the homework and Lab/Demo
sessions (20 points each). One problem each from
Chapters 5, 6 and 7.
4. You will have a formula sheet just like the one in
Introduction
Section 0 Lecture 1 Slide 4
the handout.
5. Test is Thursday February 19 1:30-2:45 in ESLC 46.
INTRODUCTION TO Modern Physics PHYX 2710
Fall 2004
Physics of Technology—PHYS 1800
Spring 2009
Review
Lecture 17 Slide 4
What Do We Need To Measure?
• What is the minimum about things we need to know?
• Where things are—a length, L
• When things are there—a time, T
• How thing interact with gravity—a mass, M
• How things interact with E&M—a charge, Q
Introduction
Section 0
Lecture 1
Slide 5
• How thing inter act with weak nuclear force
• How things interact with strong nuclear force
INTRODUCTION TO Modern Physics PHYX 2710
Fall 2004
Physics of Technology—PHYS 1800
Spring 2009
Review
Lecture 17 Slide 5
Describing Motion and Interactions
Position—where you are in space (L or meter)
Velocity—how fast position is changing with time (LT-1 or m/s)
Acceleration—how fast velocity is changing with time (LT-2 or m/s2)
Force— what is required to change to motion of a body (MLT-2 or kg-m/s2 or N)
Energy—the potential for an object to do work. (ML2T-2 or kg m2/s2 or N-m or J)
Work is equal to the force applied times the distance moved. W = F d
Kinetic Energy is the energy associated with an object’s motion. KE=½ mv2
Potenital Energy is the energy associated with an objects position.
Gravitational potential energy PEgravity=mgh
Spring potential energy PEapring= -kx
Introduction
Section 0
Lecture 1
Slide 6
In this chapter we will develop the concept of…MOMENTUM…and and its associated law of
Conservation of Momentum and apply this to collisions.
INTRODUCTION TO Modern Physics PHYX 2710
Fall 2004
Physics of Technology—PHYS 1800
Spring 2009
Review
Lecture 17 Slide 6
Newton’s Laws in Review
•
1st Law —a special case of the 2nd Law for statics,
with a=0 or Fnet=0
• An objects velocity remains unchanged, unless
a force acts on the object.
•
2nd Law (and 1st Law)—How motion of a object is
effected by a force.
– The acceleration of an object is directly
proportional to the magnitude of the imposed
force and inversely proportional to the mass of
the object. The acceleration is the same
direction as that of the imposed force.
F  ma
units: 1 newton = 1 N = 1 kg m s2
•
Introduction
Section 0
Lecture 1
Slide 7
3rd Law —Forces come from interactions with
other objects.
• 
For every action (force), there is an equal but
opposite reaction (force).
INTRODUCTION TO Modern Physics PHYX 2710
Fall 2004
Physics of Technology—PHYS 1800
Spring 2009
Review
Lecture 17 Slide 7
Central Forces and Gravity
Introduction
Section 0
Lecture 1
Slide 8
INTRODUCTION TO Modern Physics PHYX 2710
Fall 2004
Physics of Technology—PHYS 1800
Spring 2009
Review
Lecture 17 Slide 8
The Math Approach
• We are going to explore a
different kind of central force
that is no longer constant, but is
proportional to 1/r2.
ag
 k/r2
v f  v0  at or a 
v f  vo
t
1 2
 vo  vo   v f vo 
d 
t    t  v0t  at
2
 2   2 2
We will take a pragmatic approach
(hindsight
is 20-20!)
Introduction
Section 0 Lecture 1 Slide
9
We simply replace the force of the “string”
with the force of gravity
T
F
INTRODUCTION TO Modern Physics PHYX 2710
Fall 2004
Physics of Technology—PHYS 1800
Spring 2009
string
gravity
Review
k
r2
Lecture 17 Slide 9
Newton’s Law of Universal Gravitation
•
Newton recognized the similarity
between the motion of a projectile on
Earth and the orbit of the moon.
•
If a projectile is fired with enough
velocity, it could fall towards Earth
but never reach the surface.
•
The projectile would be in orbit.
•
Newton’s law of universal gravitation
says the gravitational force between
two objects is proportional to the
mass of each object, and inversely
proportional to the square of the
distance between the two objects.
Introduction
•
Section 0
Lecture 1
Slide 10
G is the Universal gravitational
constant G.
Fgravity 
INTRODUCTION TO Modern Physics PHYX 2710
Fall 2004
Physics of Technology—PHYS 1800
Spring 2009
Review
Gm1m2
r2
Lecture 17 Slide 10
Energy
Introduction
Section 0
Lecture 1
Slide 11
INTRODUCTION TO Modern Physics PHYX 2710
Fall 2004
Physics of Technology—PHYS 1800
Spring 2009
Review
Lecture 17 Slide 11
Mechanical Advantage and Simple Machines
• The mechanical advantage of a simple machine is the ratio
of the output force to the input force.
– For the pulley example, the mechanical advantage is 2.
• Work is equal to the force applied times the distance moved.
– Work = Force x Distance:
W=Fd
– Work output = Work input
• units: 1 joule (J) = 1 Nm= 1 kg m2 / s2 [ML2T-2]
Introduction
Section 0
Lecture 1
Slide 12
INTRODUCTION TO Modern Physics PHYX 2710
Fall 2004
Physics of Technology—PHYS 1800
Spring 2009
Review
Lecture 17 Slide 12
Conservation of Energy
Energy 
Energy: The potential to do work.
Conservation of Energy: The total
energy of a closed system remains
constant.
– Energy can be converted from one
form to another.
– Not all forms of energy can be fully
recovered.
Introduction
Section 0
Lecture 1
Slide 13
INTRODUCTION TO Modern Physics PHYX 2710
Fall 2004
Time 
Physics of Technology—PHYS 1800
Spring 2009
Review
Lecture 17 Slide 13
The horizontal position x of the mass on the spring is plotted
against time as the mass moves back and forth.
• The period T is
the time taken for
one complete
cycle.
• The frequency f
is the number of
cycles per unit
time. F=1/T
• The amplitude
is
Introduction Section 0
the maximum
distance from
equilibrium.
Lecture 1
Slide 14
INTRODUCTION TO Modern Physics PHYX 2710
Fall 2004
Physics of Technology—PHYS 1800
Spring 2009
X(t) = A sin (2π f t)
Review
Lecture 17 Slide 14
Impulse-Momentum Principles
Introduction
Section 0
Lecture 1
Slide 15
INTRODUCTION TO Modern Physics PHYX 2710
Fall 2004
Physics of Technology—PHYS 1800
Spring 2009
Review
Lecture 17 Slide 15
Momentum and Impulse
• Multiply both sides of Newton’s second law
by the time interval over which the force acts:
• The left side of the equation is impulse, the
(average) force acting on an object multiplied
by the time interval over which the force acts.
 v 
Fnet  ma  m 
 t 
Fnet t  mv
• How a force changes the motion of an object
depends on both the size of the force and how
long the force acts.
• The right side of the equation is the change
in the momentum of the object.
Introduction
Section 0
Lecture 1
Slide 16
• The momentum of the object is the mass of
the object times its velocity.
p  mv
INTRODUCTION TO Modern Physics PHYX 2710
Fall 2004
Physics of Technology—PHYS 1800
Spring 2009
Review
Lecture 17 Slide 16
Impulse-Momentum Principle
The impulse acting on an object produces a change
in momentum of the object that is equal in both
magnitude and direction to the impulse.
impulse = change in momentum
= p
In analogy,
Introduction
Section 0

Lecture 1
work
INTRODUCTION TO Modern Physics PHYX 2710
Slide 17
= change in energy
= ΔE
Fall 2004
Physics of Technology—PHYS 1800
Spring 2009
Review
Lecture 17 Slide 17
Rotational Motion and Forces
Introduction
Section 0
Lecture 1
Slide 18
INTRODUCTION TO Modern Physics PHYX 2710
Fall 2004
Physics of Technology—PHYS 1800
Spring 2009
Review
Lecture 17 Slide 18
Formulas We Know and Love
Introduction
Section 0
Lecture 1
Slide 19
INTRODUCTION TO Modern Physics PHYX 2710
Fall 2004
Physics of Technology—PHYS 1800
Spring 2009
Review
Lecture 17 Slide 19