All Students ( and those who pretend to be)

Let me know of any special course you took or are taking, worthwhile activities you were or are engaged in (remember, I said worthwhile) or notable achievements, so you can receive recognition from the Ridge administration, and possible inclusion in publications such as the Bridge. If you did enough good things, maybe we can even get your sentence reduced.

Seniors College Recommendations

If you had asked me to write college recs for you and you did not receive an email from me this Sunday night, get in touch with me ASAP. Spread the word to your classmates.

AP Section 2 i.e. 4th period

We will complete the lab Monday, but you better be quick: we still need to review for Tuesday's quiz.

Physics Club Web Site

The Ridge Physics Club has a website : http://www.ridgephysicsclub.com/.

If you are a member go to the site and register. Registration will be a requirement for members to get bagels soon. The purpose of registration is to improve the site as a primary means of communication among club members and with the outside world. By registering , you become eligible to post items on the website, subject to approval by me. With your help, we'll make it a useful exciting site

AP Lab

The lab report is to be formal and is due Tuesday.

AP Lab

1) Note your first graph should be a plot of position not change of position ( x not delta x). You should plot the distance from the point to the origin not to the previous point. Note that your point from which you measure , i.e. your origin, is the zeroeth point in my nomenclature

2) Time coordinate. When plotting your graphs, do not use the number of the time interval as the horizontal coordinate. use the actual time in seconds. Thus, if you chose every third point, your time interval is .05 seconds and your time scale should be labeled .05, .10, .15, .20, etc.

3) Graphing the velocity. Note that by taking the distance at time n and subtracting the distance at time n-1 from it and then dividing this difference by the time interval ( say .05 seconds) you find v. However, the v you found is not the v at time n. It is the v 1/2 way between time n-1 and time n.
Keep this in mind when you plot your v graph. So if you are looking at 5th and 6th points and your interval is .05 sec the velocity found from v= (x at .3 sec - x at .25 sec)/.05 should be plotted with .275 sec as its horizontal coordinate i.e. halfway between .25 and .30 sec.

4) Do not call the vertical axis the y axis or the horizontal axis the x axis.

5) In naming a graph use Vertical axis name vs horizontal axis name ( the vertical come first).

Chapt 1 problems

Here is some help for some Chapter 1 problems. Note solutions are not always exact but you should be able to get correct answer using the methods I present.

Problem 22 from Chap 1.

77 m + 813.8 m = 890 m or something between 889.5 and 890.5 m

Sum of two possible minimum values is 76.5 + 813.75 = 890.25

Sum of two maximum values is 77.5 + 813.85 = 891.35 so all possible values lie within 889.5 and 890.5. If we had said our answer was 77+ 813.8 = 890.8m that would have meant something between 890.75 and 890.85 which would not have included all possible values.

Problem 36 from Chapt 1 [coasts seems to mean maintains speed although most of us slow down when we coast]. In any case velocities for the zeroeth through 8th second are 0, 5,10,15,20, 25,25,25,25 m/s. Distances for the same times are: 0,2.5,10,22.5,40,62.5,87.5,112.5,137.5 m. Note you can find distance during acceleration simply by taking velocity at that time and dividing by 2 to get average during interval from start to that time then multiply by the time. This is the same as delta x = (a delta t) /2 x delta t or

delta x = a/2 delta t ^2. For last 3 seconds just add 25 m to position at previous second.

Problem 37 from Chapt 1. For easy arithmetic assume g = 10 m/s^2.

Can do this lots of ways easiest is use (vf^2-vi^2)/2a = delta x and rewrite for vf

vf = sqrt(vi^2+2a delta x)= sqrt ( 0+2x(-) 10x(-)30) = sqrt 600 = 24.4 m/s call it 24 [ note both a and delta x are negative]

for picture:

v is zero at start

at one second velocity is 10 m/s down after 1 second at 5 m down from start

at two seconds v is 20m/s down at 20 m down

watermelon reaches bottom in about 30m/((0+24.4)/2) =2.44 sec call it 2.4

40. delta t = (sqrt ( vi^2+2adelta x) –vi)/a = .37 s [note the sqrt term is just vf which comes to 6.3 m/s here, and that a is negative and delta x is positive]
just to check v avg =(10+6.3)/2 = 8.15 m/s vavg x delta t = 8.3 x .37 = 3.0 m


picture shows a =10 m/s^2 down and v = 10 at 0sec, 9 at .1 sec, 8 at .2 sec, 7 at .3 sec and 6.3 at 3.7 sec at impact.

AP Equation for delta t

In addition to your assignment, I am asking you to develop an expression for delta t if given vi, a, and delta x, starting from the two equations

delta x =( vf^2-vi^2)/2a and delta t = (vf-vi)/a.

Its ugly, but easier than using the quadratic equation to find delta t from
delta x = vi delta t + a/2 delta t^2.

Good luck and don't work too hard on it. Bring in what you've done and we'll go over it in class.

AP Lab

Here is the link for the lab we will try to do on Friday. Look it over tonight.


http://h1.ripway.com/DrCherdack/AP%20Accel%20cart%20lab.doc

AP

1) Many miscreants ( look it up if you have to) in section 1 ( period 2) managed to leave without entering their book numbers on the sheet. If you haven't entered your book number you must do so tomorrow. Without a book number I will not be able to check in your book when you return it. Your folks will be justifiably annoyed when shelling out the 180 or so bucks.

2) Those of you who have not yet turned in your old book from the summer do so ASAP so we can get this cleared up.

3) Still waiting for email addresses from about 1/3 of you.

4) Talk about miscreants, after our long talk about files and colors and in and out, most of section2 (period 4) left without depositing their summer assignments, fix this tomorrow!

Honors and AP

Here are links to schedules and assignments for our first units.

AP ( 1 link)


http://h1.ripway.com/DrCherdack/APUnit1Sched09-10r1.doc

Honors (4 links)

http://h1.ripway.com/DrCherdack/HonorsUnit1Sched09-10.doc

http://h1.ripway.com/DrCherdack/NotesEnergyFundament9-09.doc

http://h1.ripway.com/DrCherdack/HoffmanonFusion.doc

http://h1.ripway.com/DrCherdack/Fusion%20NotesR2.doc

Course Guides

Links to the course guides for Honors and AP Physics are to be found below. Please print the appropriate one of these out and read it carefully. Ask your parents/guardians to do the same.

You must bring the signature page in, signed of course. This is serious because you cannot participate in labs unless you sign the form and turn it in. Do it by class Wednesday and get 10 extra credit points.

If its not in by Friday -10 points.

The proverbial carrot and stick.

Have a good weekend and holiday.

http://h1.ripway.com/DrCherdack/Course%20Guide%20AP%20I2009-10.doc

http://h1.ripway.com/DrCherdack/Course%20Guide%20H%202009-10.doc

Welcome

Welcome to my blog

1) Please be aware that I cannot reply to your comments directly. If you want an answer, please email me at my usual bernardsboe address.

2) For AP and Honors students an extra credit opportunity:

Send me an email with a question you have about physics for 10 extra credit points. Make sure to tell me what class and period you are in. Also for honors, its 20 points for a question about fusion. Sorry, why is the sky blue is already taken.

3) Don't expect to be bribed this way very often, but check the blog daily or more often. Updates on class lessons, quiz dates, corrections to notes, problems, and most notes will be handled through the blog, at least at the beginning of the year.

AP I, Honors Physics, andHonors Research - Topics in Physics

If you are one of my students for this upcoming year please send me an email at my bernardsboe address. Please include your name and the course and period for which you are registered in the subject line of your email. Spread the word to others taking the course.

For Topics in Physics people, send me a list of topics you would like to cover this year.

Enjoy August and keep thinking physics.