Transcript People’s Physics Book

People’s Physics Book
James H. Dann
James J. Dann
Kim Knestrick
Why We Started This Project







We need a coherent theme for the course
that brings out universality
US texts too thick and unreadable
US texts far too costly
US texts have too many subtopics for each
chapter
Solved problems counter-productive
Need more problems at the AP B level
Need to refer text to lab problems
What We Did

The five Conservation Laws are the basis for
the book


Energy is a measure of the amount of, or potential for,
dynamical activity in something. The total amount of energy in
the universe is always the same. This symmetry is called a
conservation law. Physicists have identified five conservation
laws that govern our universe.
What We Did




Our book is a similar size to texts in
other countries
Giancoli has 1020 pages
French text “Physique”(2-year course)
has 350 pages; typical of Europe
Ours is comparable to international
texts
What We Did



Our text goes for just copying cost;
between $15 and $20
Compare with $120 +
Beautiful, original art work by Jason P.
Murphy
What We Did




Kept each chapter to the essentials
Momentum/Giancoli: 9 subtopics and 20
pages
Momentum/PPB: 1 1/2 pages all on
topic
Students get more understanding and
less confusion
What We Did


We count on teachers to model problem
solving
Solved problems in the text can’t
substitute for good teaching
What We Did

Variety of problems: conceptual, plug
and chug, graphical analysis, multi-step
AP style
Conceptual Problem
Below are images from a race between Ashaan (above) and Beatrice
(below), two daring racecar drivers. High speed cameras took four
pictures in rapid succession. The first picture shows the positions of
the cars at t = 0.0. Each car image to the right represents times 0.1,
0.2, and 0.3 seconds later.




a. Who is ahead at t = 0.2 s? Explain.
b. Who is accelerating? Explain.
c. Who is going fastest at t = 0.3 s? Explain.
d. Which car has a constant velocity throughout? Explain.
AP Style Problem
A positron (same mass, opposite charge as an electron) is accelerated through
35,000 volts and enters the center of a 1.00 cm long and 1.00 mm wide
capacitor, which is charged to 400 volts. A magnetic filed is applied to keep
the positron in a straight line in the capacitor. The same field is applied to the
region (region II) the positron enters after the capacitor.
a. What is the speed of the positron as it enters the capacitor?
b. Show all forces on the positron.
c. Prove that the force of gravity can be safely ignored in this problem.
d. Calculate the magnitude and direction of the magnetic field necessary.
e. Show the path and calculate the radius of the positron in region II.
f. Now the magnetic field is removed; calculate the acceleration of the positron
away from the center.
g. Calculate the angle away from the center with which it would enter region II if
the magnetic field were to be removed.
What We Did

There are problems that refer to
experiments, including design your own
Lab Problem
a. You are doing an experiment in which you are slowly lowering a tall, empty cup into a
beaker of water. T he cup is held by a string attached to a spring scale that measures tension.
You collect data on tension as a function of depth. T he mass of the cup is 520 g, and it is long
enough that it never fills with water during the experiment. The foll owing table of data is
collected:
String tension (N)
Depth (cm)
5.2
0
4.9
1
4.2
3
3.7
5
2.9
8
2.3
10
1.7
12
0.7
15
0.3
16
0
17
Buoyant force (N)
a. Complete the chart by calculating the buoyant for ce acting on the cup at each depth.
b. Make a graph of buoyant force vs. depth, find a best-fit line fo r the data points, and
calculate its slope.
c. What does this slope physically represent? (T hat is, what would a greater slope mean?)
d. W ith this slope, and the value for the density of water, calculate the area of the circular
cupÕsbottom and its radius.
b. Design an experiment using this apparatus to measure the density of an unknown fluid.
Design your own Experiment
You are to design an experiment to measure the average
force an archer exerts on the bow as she pulls it back prior to
releasing the arrow. The mass of the arrow is known. The only lab
equipment you can use is a meter stick.
a. Give the procedure of the experiment and include a diagram
with the quantities to be measured shown.
b. Give sample calculations using realistic numbers.
c. What is the single most important inherent error in the
experiment?
d. Explain if this error would tend to make the force that it
measured greater or lesser than the actual force and why.
Our Experience

Used successfully with a variety of
students at both private and public
schools
How to Use the PPB






Big Idea
Key Concepts
Key Equations
Key Applications
Problem Set
Selected Answers
You Can…




Copy the PPB in whole or in part and…
Use it as a text
Use it as a supplement
Use selected parts and/or problems
You Can…





Contribute your own problems, text,
equations,etc.
Special Needs:
Calculus-based physics
Lab problems
Graphing and graphical analysis
You Can…




Correct our mistakes
Check our answers
Send us criticisms, suggestions,
comments
Website:
http://nova.menloschool.org/~jdann/PPBweb/
PPBhomepage.htm