Transcript Physics - August 28

Mon Oct 28, 2013
1. Test (need pencil & ruler)
2. Asst: Notes pages 146152; make sure you write
the PAGE NUMBER of the
book for each part of the
notes!!
Tues October 29
1. Turn in anything from graphing
unit (worksheets, anything else?)
2. Lecture notes:
• Horizontally-shot projectiles
3. Asst: problems 2-9
**Very short unit; Nov 8th (next Friday)
is the unit test!!
MOTION OF A “PROJECTILE” or
an object moving in 2 dimensions:
• The path an object follows is called a
_________. The shape of this path is
a _________. (these are vocab words
on your next test!)
• The motion of a projectile is described
in terms of position, velocity, and
acceleration. These are all vectors
and are independent of each other.
POSSIBLE EQUATIONS:
(gee, do these look familiar?)
d=
d=
v F=
v F 2=
WHAT TO FIND IN “TYPE A”
(horizontally-shot) PROJECTILES?
• RANGE (dx)
– Displacement from the beginning of the path
to the end in the x direction.
• FINAL TOTAL VELOCITY (vFT)
– This is a vector quantity and has direction and
magnitude. Add vFx and vFy together
vectorally.
YOU MUST MAKE TWO LISTS:
VARIABLES IN THE X&Y
DIRECTIONS
x
v ox =
y
(given)
vFx = ?
dx = ?
v oy =
(if shot horiz./type A)
vFy = ?
(“range”)
dy =
(given; always neg ht for horiz./type A)
ax =
(always for projectile)
ay =
(always for proj.)
t=?
(no subscript, same in x&y)
t=?
(no subscript, same in x&y)
EXAMPLE A:
A projectile is shot horizontally at 10.0 m/s from a
height of 100. meters. What is its range and final
velocity?
velocity: 10 m/s
Step 1 – list your variables
(10 points on the test)
height: 100 m
X
Y
vox =
voy =
dx = (range) dy =
range = ?
vFT = ?
ax =
ay =
vFx =
vFy =
t=
t=
Steps 2-4, SOLVE:
2. • dy= voyt + ½ayt2
t = _____ s
4.• v = v + a t
Fy
oy
y
vFy= -_____ m/s
(but you still haven’t
found vFtotal yet! ...)
3. • dx= voxt + ½axt2
so range = _____ m
3 points for each
of these steps
on the test!
FINDING THE TOTAL FINAL
VELOCITY
Step 5: When solving for the total final velocity of
objects shot horizontally, it will always be
Note: vFx same as vox
the vector sum of the final velocities @
because ax=0 !
some degree below the horizontal.
m/s

m/s
Use the Pythagorean theorem to get the
magnitude of the resultant and inverse
tangent to get the degree:
__ _2 + __ _2 = resultant2
tan-1 (
/
) = degree
6 points for showing
diagram & work &
answer on the test!
vFtotal = ________@ _____ “below the horizontal”
Now do Asst A, numbers 2-10 all by yourself with a
chart/table of givens!
(Notice the answers are also provided!)
5 steps:
1) Make lists
2) Find time
with y list
3) Find range
(dx) with x
list
4) Find vfy with
y list
5) Find vf total
with vectors
Wed Oct 30
1. Lecture Notes – projectiles type B
2. Asst: “day 3” #2-10 on asst sheet
(Written on the asst sheet, but FYI ....)
Note # 10 is a graph & you’ll need a piece of graph
paper.
You are going to be plotting the trajectories (which
are all parabolas) of questions 1-9 and there is
an example of what you should get on the asst
sheet. Make sure you use the WHOLE sheet
of paper to make a BIG graph.
WHAT TO FIND IN “TYPE B”
(shot-at-an-angle) PROJECTILES?
• RANGE (dx)
– Displacement from the beginning of the path to the
end in the x direction.
• FINAL TOTAL VELOCITY (vFT)
– This is a vector quantity and has direction and
magnitude. Add vFx and vFy together vectorally.
• MAXIMUM HEIGHT (dy – kinda)
– Displacement from the beginning of the path to the
MIDDLE in the y direction.
– THIS REQUIRES A THIRD SEPARATE LIST!!!!
EXAMPLE B:
Suppose a ball is launched at an initial velocity of
10.0 m/s at 5.00° above the horizontal.
Find the max ht, range, and total final velocity.
max ht = ?
range = ?
vF total = ?
Step 1: YOU MUST MAKE TWO
LISTS: VARIABLES IN THE X&Y
DIRECTIONS for the range:
(10 points on the test)
x
5.0
Make sure you
understand WHY
this is true!
y
v ox =
v oy =
vFx =
vFy =
dx =
(“range”)
ax =
(always for projectile)
t=
(no subscript, same in x&y)
dy =
ay =
t=
(always 0 for type B)
(always for proj.)
(no subscript, same in x&y)
2. Start by solving for time, using the y components.
dy = voyt + ½ayt2
(we divided the whole equation by t)
t = _______ seconds
3. Now you can solve for dx (range) using the x components.
dx = voxt + ½axt2
dx =
dx =
dx = ____, so the range is ________
3 points for each
of these steps
on the test!
FINDING THE TOTAL FINAL
VELOCITY
Note: vFx same as vox
because ax=0 !

10.0sin5.0°
10.0cos5.0°
When solving for the total final velocity of objects shot
horizontally, it will always be the vector sum of the final
velocities @ some degree below the horizontal.
OK, so solve for the resultant (hypotenuse) and the angle
(using inverse tangent) on your paper right now!
Because its symmetric we know the total final velocity
will be the same as the initial speed BUT the OPPOSITE
direction.
Note: vFy same as NEGATIVE voy
because it’s a symmetric parabola!
(When it returns to it’s initial launch
position, the vertical speed is the same
as it was at launch, but it’s direction is
reversed, giving it a different velocity.)
The initial velocity was:
10.0 m/s at 5.00° above the horizontal.
Thus, the final velocity is:
10.0 m/s at 5.00° below the horizontal.
Step 4: 3 points for stating the vF total
on the test, and no points for the
work - since none is required!
Step 5: Make a list of the y values
AT THE MAXIMUM HEIGHT.
It is not necessary to list the x components at the maximum height.
y-max ht
voy =
ay =
dy-max =
vfy =
t = who cares?!?!
Do NOT use
time to find the
max height –
ever! No bad
habits in
Physics, as
this will not
work for Type
C projectiles
Step 5 cont: Remember
kinematics!
vfy2 = voy2 + 2aydy-max
dy-max = _______, so the maximum height
is ________.
Summary of steps for Type B
1.
2.
3.
4.
5.
6.
Make x & y lists for range
Find time using y list
Find range using x list
STATE vF Total
Make new y list for max ht
Find max height
Now do Asst B, numbers 2-10 ALL
all by yourself with a chart/table of givens!
(Notice the answers are given.)
Note # 10 is a graph & you’ll need
a piece of graph paper.
You are going to be plotting the
trajectories (which are all
parabolas) of questions 1-9 and
there is an example of what you
should get on the asst sheet (&
below). Make sure you use the
WHOLE sheet of paper to make a
BIG graph:
Ms. Bourke - Mon Nov 4 (no school Thurs/Fri
last week; in math lab Mon & Tues)
Test is Nov. 8th Binders due?
1. Discuss (& start) tonight’s HW part b. (see next
slide)
2. Start Computer Activity: Interactive Physics
3. Asst: Day 4 (what’s written below is ALSO on the asst sheet,
so you don’t need to copy it.)
(a) Problems on “Motion in Two Directions” ditto: on the
backside, on the bottom, part G problems 1-3. DO
THESE ON A SEPARATE SHEET, not on the wksht!!
#1 is a straight-forward Type A (horizontally shot)
problem just like day 2. Find the range and final (total)
velocity. #2 is a straight-forward Type B problem just
like day 3. Find the range, maximum height, and final
velocity. #3 is a Type A (horizontally shot) problem of a
slightly different nature. First, find the time using the ylist, just like usual. Then, use the x-list to get the initial
velocity in the x (the range is given).
(b) See instructions on the back of asst sheet “Day 4”. You
will also need a piece of graph paper.
Ms. Lewis - Physics Mon Nov 4
(no school Thurs/Fri last week; Eng or SS lab, but oly 1 day)
1.
Immediately start Computer Activity: Interactive
Physics
–
–
–
–
–
2.
Open up Interactive Physics. If you get a message “Do you want to
restart your computer now?” – choose NO, and relaunch the
program.
Pull down View, Workspace and make sure rulers and gridlines are
checked.
Pull down View, View Size and make the Window width 150 meters.
Draw a circle in the upper left of the screen (like in the upper left-most
grid, about a third the size of a grid.)
Continue following the directions on the sheet ….
Asst: Worksheet parts A-F (G is part of tomorrow's
HW); YES, write on it!
“Day 4” Asst
part A is to do problems G1-3 on a separate sheet of paper,
Part B is to ….
Get out a blank piece of paper, and …
Then you will do pebble 2, and pebble 3
THEN, you will graph the 3 pebbles’ paths:
Worksheet #1-3 hints:
•
•
•
#1 is a straight-forward Type A (horizontally shot)
problem just like day 2. Find the range and final (total)
velocity.
#2 is a straight-forward Type B problem just like day 3.
Find the range, maximum height, and final velocity.
#3 is a Type A (horizontally shot) problem of a slightly
different nature. First, find the time using the y-list, just
like usual. Then, use the x-list to get the initial velocity
in the x (the range is given).
Interactive Physics (see handout)
Open up Interactive Physics. If you get a message “Do you want to restart
your computer now?” – choose NO, and relaunch the program.
2.
Pull down View, Workspace and make sure rulers and gridlines are
checked.
3.
Pull down View, View Size and make the Window width 150 meters.
4.
Draw a circle in the upper left of the screen (like in the upper left-most grid,
about a third the size of a grid.)
5.
Click once on the circle to select it, then pull down Window, Appearance.
Make sure “Track Center of Mass” and “Track Outline” have checkmarks.
6.
Pull down World, Tracking and track the ball every 8 frames.
7.
Run your simulation, being careful to stop it right before it goes to the
bottom of the screen.
8.
Every time you want to change
something about the sim, you must
press “Reset” in the upper toolbar.
So press Reset.
Keep following the directions ….
1.
Monkey problem p.164 #44
Ms. Bourke Tues Nov 5
(2nd day in math lab)
Test is Nov. 8th
Binders due?
1. Interactive Physics – finish
• No more class time tomorrow; due Friday
4:30 PM (all 3 files saved in your I drive)
2. Asst: Day 5:
– The “Motion in Two Directions” wksht: on the
front-side parts A (multiple-choice), B (short
answer), and C (fill-in); and on the back parts DF (the 10 short conceptual problems). All of
these answers you may write ON THE WKSHT.
Mrs. Lewis, 2013: (only 1 day in lab)
no school Thurs & Fri 10/31 & 11/1
Monday Nov 4th
1)
Computer lab – Interactive Physics
2)
HW = Worksheet parts A-F
Test is Nov. 8th
Binders due!
Tuesday Nov 5th
1)
Warm-up:
a. List all 4 kinematics equations.
b. A stone is thrown horizontally at a speed of 5 m/s from the top
of a cliff 76 meters high. Set up the x & y lists to find the time,
range and final velocities. DO NOT SOLVE!
c. A player kicks a football from ground level with a velocity of 27
m/s at an angle of 15 degrees above the horizontal. Set up the
x & y lists to find the time and range. Set up the additional y list
to find the max height. DO NOT SOLVE!
2)
pass back graphing, organize binders, hand-up HW
•
3)
4)
**go over day 4 graph
Explain/start HW….
HW = Day 4 AND Worksheet Problems part G # 1-3 on a
SEPARATE SHEET of paper!
Wed Nov 6
Test is Nov. 8th;
Binders due!
1. Go over day 3 graph & collect
2. Go over Day 4 (watch demo, take notes)
& G1-3 (answers); collect
3. Draw d, v, and a vectors together
4. Turn in review wksht – Start to go over?
5. Asst: Day 6: More Projectile Problems
1-9 (but do # 1 & 7 first)
Graph from day 2 asst:
Trajectories of a Projectile
5
5 degrees
15 degrees
Height
25 degrees
35 degrees
45 degrees
55 degrees
65 degrees
75 degrees
85 degrees
0
0
Range
10
Similar graph to day 4 asst:
dx vectors and dy
vectors:
vx vectors and vy
vectors:
ax vectors and ay
vectors:
Thurs Nov 7
Unit Test (whole hour)/Quiz (only 50 pts) is Tomorrow!
1. Go over Review wksht - already turned in
2. Answers to review problems (grade #1 &
#7 like a quiz in red pen)
3. Asst: Day 7:
•
•
•
Redo 3 problems of EACH type A and B - any you
choose
plus study “extra stuff” (wrksheet & back of vectors)
PRINT OFF STUDY GUIDE, read & answer questions!
Fri Nov 8
You may copy this down AFTER the test, if you’d like!
1. Projectiles unit test/quiz (you have most of the
hour, but the test is only 50 pts instead of the usual
100) MAKE SURE YOUR CALCULATOR IS IN
DEGREES!
2. AFTER test: Turn in anything without a grademark (d,v,a vectors sheet, plus …???)
3. Asst: a) GUIDED Notes pp 88-107 & 126-132;
this means you have a 2-sided worksheet to fill
out as you read the text….
•
Sure, you could always copy someone else’s Guided Notes, and no,
we’d probably never know, but if you do so you would be missing an
IMPORTANT LEARNING OPPORTUNITY about our next unit & all of
the concepts we will be covering!