Transcript Physics - August 28

Fri Sept 20th
1. Turn in notebooks moved to next Friday!
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Make sure you have everything in your reference section
Make sure all assts are in chronological order
Makes sure nothing is in your pockets
2. UNIT TEST!
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You will need your ruler & protractor
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I will provide you with a calculator; PUT IT IN
DEGREES!
Cell phones in backpacks; both hands on desk at all
times
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3. Asst: Packet notes up to & including page 76
“Problem-solving strategy” (Write page
numbers, as before!)
Monday Sept 23
6th back in Math Lab; 1st & 3rd in lab on Tuesday
1. Collect stuff ….
2. Lecture Notes: kinematics equations,
expectations, etc (see next slide!)
3. 6th period: Computers – FINISH “Speed” write-up;
email home to print out & put in a plastic portfolio
cover
4. 1st & 3rd period: Lecture Notes on Accel of Gravity
problems
5. Asst: Practice Problems WITHIN last night’s
reading … #1-4 EVEN, 9-24 EVEN AND #23
Speed Write-ups due Friday in a plastic
report/portfolio cover
Lecture notes Kinematics part 1:
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To the right are the 4 kinematics equations
For each HW problem, you are to write out the
knowns of the problems WITH UNITS
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You are to write the unknowns, & then = ?
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the 5 variable choices are d, v0, vf, t, a
example: a = ?
You are to check that the units of all the
knowns MATCH (or else use the FLM!!)
You are to pick the correct equation based on
your knowns and unknowns.
Write the equation as you see it exactly at
right.
Write the equation again, but with the
numbers plugged in.
Solve for the first unknown.
You must then solve for the 2nd unknown too!
Answers are on the handout
Note: all variables are lower case, do not
change the order of the eqs around, show 0’s
plugged into equation where appropriate
#2 example:
v0 = 36 m/s
vF = 15 m/s
t = 3.0 sec
a=?
d=?
vf = vo + at **must write out
plug in numbers & solve
d = ½ (v0 + vf) t **write out
plug in numbers & solve
OLD – DO NOT USE!
Tues Sept 24
1st & 3rd in math lab; 6th in classroom
1. Organize binders:
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5.
Move “Current” divider back to after kinematics
Do you have the “Experiment Write-up Rubric” in your Reference
section?
Are there any more handouts or assts from the last unit that I
should have?
Questions on HW; turn in
1st & 3rd: finish Average Speed write-up
6th: Lecture Notes – gravity problems
Asst: Problems wrksht B, skip 4, 5, 6, 12
• Kinematics lecture notes part 2:
– Objects under the influence of gravity
• Lecture Notes are posted separately on
the webpage!
#11:
High popup remains in air for 6.0 seconds. Distance to top:
There are TWO okay ways to do this:
Look at it on the way up:
v naught unknown
v final = 0 (at max ht)
time = 3 sec
a = neg 9.8
d = ? (will give you a positive number)
OR:
Look at it on the way down:
v naught = 0
v final = unknown
time = 3 sec
a = neg 9.8
d = ? (should give you a negative number)
height is the absolute value of d, so it SHOULD be positive 44 meters (answer slightly wrong)
#12:
Number 12 is a THREE-STEP problem…..
1) It is dropped from 1.20 m:
v naught = 0
d = NEGATIVE 1.2
a = negative 9.8
v final = ?? (this is question a)
NOTE ****** If you use vf^2 = vo^2 + 2 ad, then to solve this you have to square root as the final step.
BUT, a square root ALWAYS has 2 answers, both positive & negative!
In this case, the object is going DOWN, so the correct answer is the negative one!
LOTS of points taken off on the test for that, when its done wrong!
IF you ever find yourself trying to take the square root of a negative
number, YOU'VE DONE SOMETHING WRONG!
It is almost always that you've missed something that is supposed to be
negative.
Remember: down is negative!
2) It rebounds to a height of 1.00m:
v final = 0 (at max ht)
v naught = ? (this is answer b, and should be positive, because its UP)
a = negative 9.8
d = positive 1.00
So if it falls, the d is down, AND the v final is down, so both of those are
negative.
3) In the split-second while it is in contact with the ground, what is the accel?
Well, the v final from part a is now the v initial of THIS part, right?
AND, the v naught from part b is now the v final of this part, right?
(Close your eyes and concentrate on what's happening and THINK about that!)
So, now you know both v's, and know t = 0.010 sec, and can get accel.
NOTE - make sure your math works out EXACTLY CORRECTLY to get my answer, or you've done something slightly wrong!
On the unit test, I usually end up taking off lots of points for significant
figures and NEGATIVE signs, so pay careful attention to those so that
you don't miss those points.
Wed Sept 25
(collab day)
1.
4 parts: horizontal problems, vertical problems, concept questions
from sheet 3, last question is about the experiment
Do these 2 problems in your lecture notes quietly
1.
2.
A student pushes upwards off a diving board that is 10.0 meters above the
water at 2.00 m/s. What is their total time in the air, and their final velocity right
before they hit the water?
A space ship is traveling 25 m/s, when it starts experiencing an acceleration of
-4.0 m/s2. What is its velocity and displacement after half a minute?
Questions on yesterday’s asst (wksht B)?
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Test Friday October 4th
9b) d = - 30 m; 11) if you solve it for the way down (easier), you get - 44 m,
but it actually “rose” + 44 m; initial & final vel = ± 29 m/s 13b) d = - 78 m;
16a) this question did NOT ask “total time in the air”, so the answer is
only 2.8 seconds, but if it DID ask “total time in the air” you would have
to multiply by 2 to get 5.6 seconds!
Work on today’s asst:
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3.
Brief NOTES from the front side of sheet 4 (“Accel due to
Gravity”)
Wrksht B 4-6 (4) 1.2 s, -2.0 m/s; (5) -78 m/s, -310 m; (6) -15.3 m/s; 1.56 sec
on the third SHEET of paper in your packet, the front side:
Concepts 8-10, 6-8; and on the same page, Problems 9, 17a,
18, 20, 22, 24
**If you have more time, work on Thur’s asst: wrksht C 1320** ALL, 2-12 even (**important!!!!)
Test Friday October 4th
Thurs Sept 26
4 parts: horizontal problems, vertical problems, concept questions
from sheet 3, last question is about the experiment
1. Binders: did you … put Experiment checklist in
Reference; move Current divider BACK behind
last unit; do you have ALL the daily agendas?
– COLLECTED FRIDAY
2. Go over yesterday’s HW questions (concepts!)
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Brief NOTES Accel due to Gravity
Wrksht B 4-6 (4) 1.2 s, -2.0 m/s; (5) -78 m/s, -310 m; (6) -15.3 m/s; 1.56 sec
on the third SHEET of paper in your packet, the front side: Concepts 8-10,
6-8; and Problems 9, 17a, 18, 20, 22, 24
3. QUIZ
4. Asst: worksheet C 13-20** ALL, 2-12 even
(**important!!!!)
5. Write-ups due too!
Test Friday October 4th
Fri Sept 27
1.
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3.
Binders collected today at end of period!!!
Look at last test briefly.
Self-correct “Quiz” in RED.
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(a)
(b)
4 parts: horizontal problems, vertical problems, concept questions
from sheet 3, last question is about the experiment
Basically its 1 point for each known (as long as you have a negative sign when there should
be one) and each unknown (must have a question mark!)
Its 1 point for each correct equation (it does not necessarily have to be the same one I used!)
used to solve for an unknown
Its 1 point for showing your math-work/numbers plugged into each of the equations
Its 1 point for the correct answer WITH units & significant units (it must be negative if mine is;
it may be SLIGHTLY different than mine if clearly supported by your equation & your math!)
Give yourself a total score and a percent (out of how many YOU completed)
Quizzes are to be turned in after you are done.
With the rest of your class time, start the “Prelim exercise” in
preparation for Monday’s experiment – EACH person collects their
OWN data quietly from the picture and to the 0.1 mm. (We will
actually roll things down incline planes in class Monday and collect
REAL data too!)
HW:
finish prelim exercise (all data & 2 graph sketches)
Sheet 3, right column # 9, 12, 13 + back of sheet 3 (ditto “A”) #2-4
(That’s 6 kinematics problems total)
Ditto A #4b) How far move AFTER 3.6 sec
Test Friday October 4th
Mon Sept 30
4 parts: horizontal problems, vertical problems, concept questions
from sheet 3, last question is about the experiment
1. In class: Average Accel
experiment
2. HW: ditto D (find both unknowns)
• skip: 33, 34, 38, 41;
• do 30-32, 35, 37, 39-40; 54-57 & 60
• EMAIL ME ANY QUESTIONS
ABOUT THESE; there won’t be time
in class to answer questions! (Odds
are that the one you can’t do will
appear on the unit test!)
Tues 10/1
***SIT WITH YOUR LAB PATNERS FROM
FRIDAY!***
1. Collect HW? (ditto C and D??)
2. Computer lab – Average Accel data
3. HW a: Experiment Write-up Title-Procedure
(see email for hints)
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Handwritten, neatly, skipping lines, bring in tomorrow
4. HW b: PRINT OUT STUDY GUIDE!
Test Friday October 4th
4 parts: horizontal problems, vertical problems, concept questions from sheet 3,
last question is about the experiment from today
Wed 10/2
SIT WITH LAB PARTNERS AGAIN!
1.
Collect HW? (ditto C and D??)
2.
Computer lab – Average Accel data
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3.
CHECK DATA against sheet handed out yesterday (checklist)
Email data home (will need to be printed on color printer!)
Work on hand-written write-up (Results & Conclusions) when done w/ data
Asst: Redo ditto C probs 13-20 ALL, and 1-12 odd (new, better sheet
provided**)
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b.
c.
d.
4.
List knowns & unknowns
Write the equation before you plug numbers in!
Plug numbers in and solve
TAKE THIS LIKE A PRACTICE TEST! (We will grade it like one tomorrow!
MAKE SURE STUDY GUIDE IS PRINTED OFF!
Test Friday October 4th
4 parts: horizontal problems, vertical problems, concept questions from sheet 3,
last question is about the experiment from yesterday & today
Thurs 10/3
1.
2.
Hand back papers
Grade ditto C as “Practice test” **
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Teacher will read off knowns & unknowns (+ 1 for each that is correct)
1 point for each correct equation used, IF KNOWNS ARE CORRECT!
1 point for showing math-work/numbers plugged into ea. equation
Teacher will read off answer (1 point ea. IF has units & significant figs)
***Discuss how to do #20 if “descending” instead
3.
Go over Preliminary Exercise & Study Guide (see next slides)
4.
HW:
(a) Finish Average Acceleration Write-up if must
(b) Retake the quiz from last week, covering up the answers. Check it
after you’re done! Watch the tricky times, and all those negative
signs!
(c) Study the concepts (see Study Guide)
Study Guide for Unit 2 (Kinematics) Test:
A)
Approximately 5 questions dealing with objects moving horizontally. Study packet problems about
people, cars, trains, planes, etc.
Approximately 5 more questions dealing with objects moving vertically, where the acceleration is always
–9.8 m/s2. Study ditto B (and your quiz!) in particular.
(Ditto C has a nice combination of both horizontal & vertical problems, similar to what you might see on the
test. However, be careful of the answers given – both numerically and because of sig figs.)
B)
ALSO: Some “Conceptual questions:
Know about the velocity(s) of an object as it is shot straight up into the air AND as it falls back down. Use
the words positive, negative, speeding up, zero, and slowing down.
Know about the acceleration of an object as it is shot straight up into the air AND as it falls back down.
Know about how the acceleration of gravity effects the total time in the air & the height they would be able
to reach. (ie: if it were less than 9.8 as it is on the moon, would time in the air be more or less, would
height it attains be more or less?)
What falls faster, a heavier object or a lighter object? (Hint: think about the acceleration of gravity in both
cases. Is this a trick question?)
C)
Know about your Average Acceleration experiment: (Pictures and examples are always helpful to show
complete understanding.)
In 5 words or less, what did you do? (hint: cart, incline)
What data was collected by the computer/LoggerPro/Photogate/picket-fence system (hint: look at the axes
of your graphs!)
Of the two answers for b above, what was graphed on which axis (use the words dependent &
independent)
How did you determine the acceleration from this graph (what did you do to it EXACTLY and what did you
look at SPECIFICALLY).
What is the definition of acceleration?
How does this equation (in e above) compare with what you looked at on the graph to determine the
acceleration? (Hint: Slope = ___ / ___ )
Friday Oct 4th
1. Test: need pencil & calculator
Note: Essay make-up test if absent for 2 tests in a semester.
I’ll be coming around asking you to show me your hands to
make sure you don’t have the equations written on them!
2. HW: Roller coaster
Note: need handout + 3 sheets graph paper
HW b: NOTES in book pages 38, 40, 42, 62
(copy all graph figures/pictures AND the captions that go with them! This is
the most important part of those notes!)