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Physics 101: Conceptual Physics

That’s how we roll.

About Me

•  My office is in Science 356 •  Come say hello! •  Best place to ask questions is office hours

– WF 2-4PM, T 10AM-1PM, or by appointment •  Best way to contact me is email

–  jfielder@sfsu.edu – put “Phys 101” in the subject line

http://www.physics.sfsu.edu/~jfielder/Phys101S15.html

Goals For This Class

Help you develop: •  a basic understanding of the central ideas

of physics •  the ability to solve basic problems using

physics concepts •  a real-world perspective for how physics is

connected to your daily life

Administrative Stuff •  Enrollment

– Very Full! – Prerequisites

•  Lab (Physics 102) •  Textbook •  Mastering Physics

– Course ID: fielder – 2-week free trial period –  Introductory assignment due soon! Register

as soon as humanly possible

Participation

•  15% of your final grade is class participation – Short writing assignments – Group activities – Voting

•  If you miss class, you cannot make up the participation credit

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Homework

•  About 1 assignment per week •  Problems from textbook •  Working in groups is encouraged, but the

work you turn in must be your own.

•  Homework is 30% of your final grade (so each assignment is worth about 2%)

Exams

•  3 midterms (15% each) and a final (25%) •  Lowest midterm score is dropped •  multiple choice and some short problems •  Exam dates are not flexible

•  DO NOT MISS EXAMS! THERE ARE NO MAKEUPS!

Grades

•  Homework 30% •  Participation (15 x 1% each) 15% •  Midterms (top 2 x 15% each) 30% •  Final Exam 25%

I do not offer extra credit, but exams and overall grades may be curved. If you need to talk about your grade in detail, email me to make an appointment.

Syllabus Questions?

The Montillation of Traxoline

It is very important that you learn about traxoline. Traxoline is a new form of zionter. It is montilled

in Ceristanna. The Ceristannians gristerlate large amounts of fevon and then brachter it to quasel traxoline. Traxoline may well be one of our most

lukized snezlaus in the future because of our zionter lescelidge.

(attributed to the insight of Judy Lanier)

The Montillation of Traxoline It is very important that you learn about traxoline. Traxoline is a new form of zionter. It is montilled in Ceristanna. The Ceristannians gristerlate large amounts of fevon and then brachter it to quasel traxoline. Traxoline may well be one of our most lukized snezlaus in the future because of our zionter lescelidge.

Directions: Answer the following questions in complete sentences. Be sure to use your best handwriting. 1. What is traxoline?

2. Where is traxoline montilled?

3. How is traxoline quaselled?

4. Why is it important to know about traxoline?

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A Commonly Held Incorrect Model of a Student’s Conceptual Framework

tabla rasa

A Commonly Held Incorrect Model of Teaching and Learning

If a bowling ball and a baseball are both dropped from the same height at the same time, which one will reach

the ground first?

A.  The bowling ball, because it has more mass B.  The baseball, because it has less mass C.  The bowling ball, because it is larger in size D.  They will reach the ground at about the

same time E.  None of the above

Class Discussion: What do you think science is?

Evaluating and expressing our notions about science

Find a partner or two, and answer the following questions after

discussing them and coming to an answer you can all agree on.

1.  What are the differences between a hypothesis, a theory and a law in science?

2.  What is required for an experiment or observation to be “scientific”?

3.  Do scientists ever get it wrong? If so, do they try to fix it, and how?

Laws, Theories, and Hypotheses •  What is the

difference between a hypothesis, theory, and law?

•  How do scientists use these words differently from the public?

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The Scientific Method

1.  Which problem do you want to solve? 2.  Form hypothesis 3.  Design experiment and make predictions 4.  Perform experiment/observations 5.  Do the data support the hypothesis? ->Revise or reform hypothesis based on results

So what is Science?

•  Questions •  Models •  Tests & Predictions •  Evaluation •  Building up to a set of

“rules”: Laws or Theories

This course covers the basics:

•  Different branches of physics: motion, matter, heat, light, sound, electricity, magnetism, nuclear reactions, and relativity

•  How to solve basic problems •  Not just the “what” but the “why” behind it

(or as much of the “why” as we currently understand…)

Physics can be BIG!

SI Units: The Système International or “mks”

•  Length: meter (m) •  Mass: kilogram (kg) •  Time: second (s) •  Force: newton (N) •  Energy: joule (J) •  Current: ampere (A) •  Temperature: kelvin (K)

Metric System (Units of Length) •  Everything is based on the meter (m)

– 1 kilometer (km) = 1000 m = 103 m – 1 centimeter (cm) = 0.01 m = 10-2 m – 1 millimeter (mm) = 0.001 m = 10-3 m – 1 nanometer (nm) = 0.000000001 m = 10-9 m

•  Good estimates: – 1 meter is about 3.3 feet – 1 inch is 2.54 centimeters – 5 miles is about 8 kilometers

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Why unit conversions are important! Units & Conversions

•  Example: How many seconds are in a year?

Scientific Notation & Significant Figures

•  How precisely do we know a number? •  Example: How many days are there in a

year?

Which of the following correctly expresses 186,000 m/s in scientific

notation, to three sig figs?

A.  18.600 x 104 m/s B.  186.0 x 103 m/s C. 1.86 x 105 m/s D. 1.86 x 103 m/s

An American football field is 300 feet long (not counting the end

zones). Roughly how long is this in meters?

A. About 91 meters B. About 99 meters C. About 910 meters D. About 9,900 meters

Newton’s 1st Law & Inertia (Chapter 2)

Get out your voting cards for reading check.

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Which scientist used inclined planes to study motion?

A. Copernicus B. Aristotle C. Newton D. Galileo E. None of these scientists used inclined

planes to study motion.

Which of the following is the SI unit of force?

A. pound B. newton C. kilogram D. meters per second

Which of the following best describes what inertia is?

A. The tendency of objects to resist changes in their motion

B. The tendency of objects to stay standing still

C. The tendency of objects to slide downhill D. The tendency of objects to slow down

after they’re pushed

Which of the following explains what is meant by “net force”?

A. The strength of the force of gravity acting on an object

B. The strength of all forces combined acting on an object EXCEPT gravity

C. The strength of all forces combined acting on an object

Newton’s 1st Law

An object at rest will remain at rest and an object in motion will remain in uniform motion unless acted upon by a force. •  Uniform motion: constant speed in a

straight line. •  Also called the “law of inertia”

Newton’s 1st Law

Object at rest (not moving) then

No force on object

then

Uniform motion

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So what is “inertia”?

•  The tendency of an object to “keep doing what it’s already doing”

•  Amount of inertia depends on the amount of mass. Careful, though: Inertia is not the same thing as mass, and inertia isn’t a force either!

Typical Force Sizes

Net Force •  When several forces act on an object, the forces

combine to produce a net force or total force. •  If the individual forces are all in the same

direction, the size of the net force is just the sum of the individual forces.

•  Use arrows to symbolize force vectors: length of arrow shows size of force, direction of arrow shows direction of force

3 N 5 N

8 N

Combining Forces

•  Direction counts! •  If two forces are in the SAME direction,

they ADD together •  If two forces are in the OPPOSITE

direction, the smaller one SUBTRACTS from the larger one

Vector Notation

•  When handwritten, use an arrow A •  When typing, use boldface: A •  To write just the magnitude use italics: A

•  The “Σ” symbol (capital sigma) means “the sum of”. To describe adding up all the forces on an object, write ΣF or ΣF

How much net force is acting on the box?

A. 0 N B. 5 N C. 10 N D. 15 N E. 20 N