Transcript 13.11.19APWeek15Energy

AP Physics
Monday 13.11.18
Standards: b2b2 write down
vector equation that results from
Newton’s 2nd Law
Warm Up
Did you try to solve the rest of the AP
Review Questions? If yes, were you able
to figure them out? If no, what did you
do to prepare for the test.
Objective: SWBAT score
equivalent of score 3 on the test.
Agenda
1. Warm Up
2. Take Forces Test
Homework
Lab Report Due Tomorrow
AP Physics
Tuesday 13.11.19
Standards: 1a1,1a3 Students
understand the definition of
work.
Objective: SWBAT solve
problems involving work.
Warm Up
This was a problem on the test. Find the
two unknowns.
Fy=?
Fx=?
W
W=50N
30°
Agenda
1. Warm Up
2. Review Test
3. Work Notes
4. Work Guided Practice
Homework
E#1
AP Physics
Wednesday 13.11.20
Standards:
1a4: Use Scalar product to calculate the
work performed by a specified constant
force.
Objective: SWBAT represent work
graphically by dragging an object a certain
distance.
Warm Up
Find the work done when a 100 N
force 50 degrees above the horizontal
causes an object to move 40m in the
horizontal direction. See diagram
below.
100
N
50°
40m
Agenda
1. Warm Up
2. Review Homework
3. Guided Practice – Work
Homework
#E2
Warm Up
Find Work.
AP Physics
Thursday 13.11.21
Standards:
1a4: Use Scalar product to calculate the
work performed by a specified constant
force.
Ojective: SWBAT 1a4: Use Scalar product to solve
70N
60°
120m
problems involving work
Agenda
1. Warm Up
2. Review HW
3. Review Lab
4. Solve Work Problems
Homework
Finish HW #E2
AP Physics
Friday 13.11.22
Standards: 1b3 Calculate the change
in speed or kinetic energy that results
from performing a specified amount of
work on an object.
Objective: SWBAT will be able to solve
problems involving Kinetic Energy
Agenda
1. Warm Up
2. Review HW
3. Collect Lab Reports
4. Kinetic Energy & Work
Warm Up
Find the work done by a 2000kg elevator
that raises its payload 10 meters while
moving at a constant velocity?
Homework
Thanksgiving HW
HW #E3
Next Homework Packet Due
Monday: Thankgiving HW, E1E3 & Any other previous
assignment you haven’t turned
in.
AP Lab Write Up Rubric
Section
4
3
2
1
Question/Hypothesis
The central question the lab is
asking is stated along with a
plausible hypothesis
The central question is stated
and something resembling a
hypothesis is stated
Only the central question is
stated
The section is missing or
contains the wrong central
question.
Materials/Procedures
The procedures are written
step by step in complete
sentences and the materials
are clearly listed.
The procedures and materials
are listed but unorganized. The
procedure does not explain the
lab
Either the procedures or the
materials are incomplete.
Only procedures are present,
or only materials are present.
Data Collection
The lab contains a table and a
graph that represents the data
accurately and is labeled
correctly with the equation of
the line written.
The lab contains a table and a
graph but it may be missing
some labels and the graph may
not be done correctly.
The lab is missing a graph
completely.
The data is incomplete.
Calculations
Students have all calculations
completed, with work shown,
and they are correct.
Students have all calculations
completed and at least half are
done correctly and all work is
shown.
Students do not have all
calculations completed, and
little work is shown.
Calculations section is mostly
or entirely missing.
Analysis
The student gives evidence
from their lab data why their
hypothesis is true, false, or
inconclusive. The discuss the
relationships between the
variables that were graphed
and if linear they write down
the equation of the line.
The students gives evidence
from their lab data and
attempts to prove that the
hypothesis is false, true or
inconclusive, but the data is
misapplied and doesn’t support
their claim. For linear graphs,
no equation is given.
This section discusses whether
the hypothesis is true,
inconclusive, or false but no
data is used to support the
hypothesis and any reference
to the graph or the data is too
general to be helpful.
This section is omitted or the
student may mention the
hypothesis and its validity, but
doesn’t explain or the
explanation is not plausible
Conclusion
The conclusion includes a
summary of your lab results,
(which will include numbers or
equations), gives %error and
discusses sources of error. It
also gives a suggestion about
how to improve the lab.
The conclusion includes a
summary of your lab results. It
includes data. % error is given.
Either and least 1 source of
error discussed or a suggestion
is given to improve the lab.
The conclusion includes a
summary and either % error, or
mentions types of error, or
mentions improving the
experiment.
The conclusion is omitted or
only includes a brief summary.
What is Work?
Work is done when…
F
d
F
d
What is work?
Work is not done when?
Fg
Fap
A
B
d
FN
Fap
Now make up a definition of work,
write it down to turn in, and prepare to
discuss.
Work and the Dot Product
Dot Products occur when you multiply 2 vectors (in this case F & d) and your
answer is a scalar (it has no direction.)
W = F ·d
W = Fd cosqab
-A. This equation means that if I
lift up a box by applying a Force,
I will not be able to move it to
the right with my lifting Force.
-B. If I push the box to the right with enough
Force to move the box, it will move to the
right. I will have done work!
-C. If is drag a box from a string across the
ground, only the horizontal component of the
Force I apply will make the box move and
therefore do work.
θ
Work Practice E#1
Find the work done by the Forces in each diagram? Pay attention to
the direction of each of your vectors. It matters.
30N
90m
1.
20m
6.
40N
125m
1N
2
40N
10°
7.
3
40N
20m
30m
8.
20m
5m
70N
4.
70N
9.
80N
5.
40°
135°
40m
40N
20m
55N
10.
10m
35°
Guided Practice
1. A 2000kg box is carried 4m in the air across a warehouse
that is 100 m long by a forklift? If it takes 2000 N to move it,
how much work is done by the forklift? If the forklift then
puts the box down on the ground, how much work is done
by gravity on the box?
2. A little box is pulled a distance D by a string at an angle θ by
a child distance with a Force F. What is the work done by
the child?
Work Practice E#2
1.
2.
3.
4.
5.
6.
7.
A child pulls a wagon full of toys using a rope over his/her shoulder. If the angle of the rope is 60
degrees above the horizontal, how much work will s/he do if he moves the cart 12m after applying
320 N of Force?
(ex)The largest palace in the word is the Imperial Palace in Beijing, China, Suppose you were to push
a lawn mower around the perimeter of a rectangular area identical to that of the palace, applying a
constant horizontal force of 60.0 N. If you did 2.05x105 J of work, how far would you have pushed
the lawn mower? If the Imperial Palace is 9.60x102 m long, how wide is it?
(1) Lake Point Tower in Chicago is the tallest apartment building in the United States (although not
the tallest building in which there are apartments). Suppose you take the elevator from street level
to the roof of the building. The elevator moves almost the entire distance at constant speed, so
that it does 1.15x105 J of work on you as it lifts the entire distance. If your mass is 60.0 kg, how tall
is the building. Ignore the effects of friction.
(3) A hummingbird has a mass of about 1.7g. Suppose a hummingbird does 0.15 J of work against
gravity, so that it ascends straight up with a net acceleration of 1.2m/s2 How far up does it move?
3
(8) The largest mincemeat pie ever created had a mass of 1.02x10 kg. Suppose that a pie with this
mass slides down a ramp that is 18.0 m long and is inclined to the ground by 10.0°. If the
coefficient of kinetic friction is 0.13, what is the net work done on the pie during its descent?
(9) The longest shish kebab ever made was 881 m long. Suppose the meat and vegetables need to
be delivered in a cart from one end of this shish kebab’s skewer to the other end. A cook pulls the
cart by applying a force of 40.00 N at an angle of 45.00° above the horizontal. If the force of
friction acting on the cart is 28.00 N, what is the net work done on the cart and its contents during
the delivery?
3
(11) width of 78 m. the flag’s mass is 1.24x10 kg, which may explain why the flag has never been
flown from a flagpole. Suppose this flag is being pulled by two forces: a force of 8.00x103N to the
east and a force of 5.00x103 N that is directed 30.0°south of east. How much work is done in
moving the flag 20.0 m directly south?
Kinetic Energy Practice
1.
2.
3.
4.
#E3
(Ex) Silvana Cruciata from Italy set a record in one-hour running by
running 18.084 km in 1.000 h. If Cruciata’s kinetic energy was 694
J, what was her mass?
(2) The fastest helicopter, the Westland Lynx, has a top speed of
4.00x102 km/h. If its kinetic energy at this speed is 2.10x107 J,
what is the helicopter’s mass.
(7) The brightest, hottest, and most massive stars are the brilliant
blue stars designated as spetral class O. If a class O star with a
mass of 3.38x1031kg has a kinetic energy of 1.10x1042J, what is its
speed? Express your answer in km/s (a typical unit for describing
the speed of stars)
(6) Susie Maroney from Australia set a women’s recond in longdistance swimming by swimming 93.625 km in 24.00 h.
1.
2.
What was Maroney’s average speed?
If Maroney’s mass was 55 kg, what was her kinetic energy?
Work Lab
Work = Force * distance
-- Objective: Determine the total work done by the Force
Meter, after putting successively greater masses on the
ForceMeter and graphing the data. You must find the total work
from the graph (not by calculations)
-- Materials: homeade Force meter, ruler, masses
--