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 experi ment in which you are slowly low ering a tall , empty cup into a beake r of water. The cup is held by a string attached to a spring scale that measu res tension . You collect dat a on tension as a function of depth . The mass of the cup is 520 g, and it is long enough that it neve r fills with water during the experiment. The foll owing table of data is collected:
String tension (N)
5.2 4.9 4.2 3.7
Depth (cm)
0 1 3 5
Buoyant f orce (N)
2.9 8 2.3 1.7 0.7 0.3 0 10 12 15 16 17 a.
b.
c.
d.
Complet e the chart by calculat ing the buoyant force acting on the cup at each depth. Mak e a graph of buoyant force vs. depth, find a best-fit line for the dat a points, and calculate its slope . What does this slope physically represent? (That is , what would a
greate r
slope mean?) With this slope , and the value for the density of water, calculate th e area of the circula r cupÕs bottom an d its radius. b.
Design an experimen t 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.
c.
Give sample calculations using realistic numbers.
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