Transcript Powerpoint - generative design center

An Introduction to Net Force and
Changes in Motion
tinyurl.com/newtonia
Newtonia: What TEKS?:
6.8B identify and describe the changes in position, direction, and
speed of an object when acted upon by unbalanced forces
6.8D measure and graph changes in motion;
6.8D Students will investigate the relationship between force
and motion using a variety of means, including calculations
and measurements
8.6A Demonstrate and calculate how balanced forces change
the speed or direction of an object's motion
8.6B Differentiate between speed, velocity, and acceleration
8.6C Investigate and describe applications of Newton's law of
inertia, law of force and acceleration, and the law of actionreaction such as vehicle restraints, sports activities,
amusement park rides, Earth's tectonic activities, and rocket
launches.
Table of Contents
What is it?: An introductory lesson sequence for Newton’s Laws Using a Computer
Simulation (Url: tinyurl.com/Newtonia)
What is needed?: Best if each student or pair of students have a computer with ability to
connect to internet & copies of handouts (or respond in notebook). Can be done
with just a teacher machine running simulation. Doc camera can be useful for
sharing student results and discussing patterns. Pages 3&4 and pages 6&7 can be
printed front-and-back to hand out to students. Additional copies of 6&7 can be
used for still more challenges. Browser: Use Firefox or Explorer (not Chrome)
Introductory Questions (To be completed before activity)
– for handout, print 4 to a page
– or use pdf pages
Activity – Introductory notes/observation followed by a shared challenge and possible
additional challenges.
Revisit Selected Introductory Questions plus Additional Questions (could be homework
or used in class).
Additional Resource – Acceleration
Assessment Items (& Key) – Released TAKS Item and Non-Dichotomous Multiple Choice
Item
Period:
[1] Velocity (How Fast) Graphs – Press Go and
experiment with the N S E and W buttons to see
what they do. Press Go again to pause the
simulation.
(a) What do the lines on this graph represent? A higher line
(above or below zero) means what? Where is zero for
both lines?
Name:
START
PAUSE
Note: You must press
the Go button to start
the simulation. To
pause, press the Go
button again.
(b) Which color (red or blue) goes with which directions? N/S
vs. E/W?
(c) If you don’t press a button (don’t apply a Net Force)
describe the motion:
2
Objective - PART A: __Get the Donut to Move Diagonally Up and to the Right_______
Tally Marks
(i)
Totals
+/VERTICAL
N (+)
combine
S (-)
HORIZONTAL
E (+)
combine
W(-)
Sketch the
velocity
graphs for
Part A (use
dashes for
blue line).
The end of
the sketch is
the most
important.
Objective - PART B: ___Now get the Donut to Move Horizontally to the Right ______
Additional Tally
Marks
Additional
Totals
VERTICAL
N (+)
(ii)
S (-)
combine
HORIZONTAL
E (+)
W (-)
+/-
combine
Overall Totals for Each Direction:
The # from (i) + the # from (ii)
N (+)
S (-)
E (+)
W (-)
+/VERTICAL
Sketch the
velocity
graphs for
Part B (use
dashes for
blue line).
The end of
the sketch is
the most
important.
Could you end up with these same
totals but with different values for (i)
& (ii)? Explain:
combine
HORIZONTAL
combine
Name:
Partner(s):
Period:
Discussion and Other Possible Newtonia Objectives
Group 1 Results
Group 2 Results
What patterns do we notice in (a), (b)
and then in the totals?
What other Two-Part Objectives
might we try?
Discussion
[1] Use document camera or copy selected tables on white board to
share results from different groups.
[2] In addition to individual solutions, what patterns emerge in terms
of part (a) getting the donut to move diagonally, (b) then
horizontally and then the totals from (I + ii ) after it is moving
horizontally?
[3] A way of clarifying the patterns is to ask how could we tell if a
result would NOT work? Hinting at the possibility of additional
forces, if an object is moving horizontally but later is observed to
be moving downward (gravity) or slowing (friction) what
additional forces are present? Discuss in terms of NET force ≠ 0
causing an acceleration (≠ 0) or a change in motion.
Objective 2: (a) Move and then stop (b) Move again and then stop
Objective 3: Start off moving at a constant velocity in one direction and
then: (a) Change the direction and speed of the object (b) Return
to the original velocity (original direction and speed)
Objective 4: Turn on Friction by dragging (or clicking) slider to 1. Then:
(a) Get the object to move at a relatively constant velocity
(b) Now get the object to stop
How are the patterns from others likely to be the SAME and also
DIFFERENT from what you got?
(relatively constant)
Objective - PART A: _____________________________________________________
Tally Marks
(i)
Totals
+/VERTICAL
N (+)
S (-)
HORIZONTAL
E (+)
W(-)
Sketch the
velocity
graphs for
Part A (use
dashes for
blue line).
The end of
the sketch is
the most
important.
Objective - PART B: _____________________________________________________
Additional Tally
Marks
Additional
Totals
VERTICAL
N (+)
(ii)
+/-
S (-)
HORIZONTAL
E (+)
W (-)
Overall Totals for Each Direction:
The # from (i) + the # from (ii)
N (+)
+/VERTICAL
Sketch the
velocity
graphs for
Part B (use
dashes for
blue line).
The end of
the sketch is
the most
important.
Could you end up with these same
totals but with different values for (i)
& (ii)? Explain:
S (-)
E (+)
W (-)
HORIZONTAL
Name:
Partner(s):
Period:
Objective - PART A: _____________________________________________________
Tally Marks
(i)
Totals
+/VERTICAL
N (+)
S (-)
HORIZONTAL
E (+)
W(-)
Sketch the
velocity
graphs for
Part A (use
dashes for
blue line).
The end of
the sketch is
the most
important.
Objective - PART B: _____________________________________________________
Additional Tally
Marks
Additional
Totals
VERTICAL
N (+)
(ii)
+/-
S (-)
HORIZONTAL
E (+)
W (-)
Overall Totals for Each Direction:
The # from (i) + the # from (ii)
N (+)
+/VERTICAL
Sketch the
velocity
graphs for
Part B (use
dashes for
blue line).
The end of
the sketch is
the most
important.
Could you end up with these same
totals but with different values for (i)
& (ii)? Explain:
S (-)
E (+)
W (-)
HORIZONTAL
Name:
Partner(s):
Period:
Name: ___________________________ Period: ________
[1] For Newton, a NET FORCE (imbalanced force
or Net Force ≠ 0) causes a CHANGE IN MOTION
(change in velocity) or ACCELERATION.
(a) How can you tell from just looking at the velocity graph which
button you pressed? (be sure to mention color and direction +/-)
N:
S:
(ii) Which
results in a
W:
change in
motion
(velocity)
E:
(b) Using the SUMMARY, consider your answers to these questions.
For each scenario write if there is a non-zero NET force (Hint: Is there a
change in motion?):
(ii) An
acceleration
(≠ 0)
(i) A Net Force
(≠ 0) N causes
Summary
Net Force (≠ 0) ? (Y/)N)
How do you know?
Net Force (≠ 0) ? (Y/)N)
How do you know?
Net Force (≠ 0) ? (Y/)N)
How do you know?
[5]
Circle response for each section of graph
(a) Velocity
Acceleration
Net Force
(b) Velocity
Acceleration
Net Force
(c) Velocity
Acceleration
Net Force
(d) Velocity
Acceleration
Net Force
(e) Velocity
Acceleration
Net Force
increasing
positive
positive
increasing
positive
positive
increasing
positive
positive
increasing
positive
positive
increasing
positive
positive
::
::
::
::
::
::
::
::
::
::
::
::
::
::
::
decreasing
negative
negative
decreasing
negative
negative
decreasing
negative
negative
decreasing
negative
negative
decreasing
negative
negative
::
::
::
::
::
::
::
::
::
::
::
::
::
::
::
constant
zero
zero
constant
zero
zero
constant
zero
zero
constant
zero
zero
constant
zero
zero
c
0 a
b
d
e
[6] (a) Create a story about an object and state explicitly where the
object experiences a net positive (+), a net negative (-) and a net
zero (0) force. Be sure to say how the object starts off moving.
0
(b) Draw a graph for this story and label the corresponding parts with +/-/0. Be sure to say how the object starts
off moving.
Introductory Questions
Newtonia - Intro Questions
© 2008-11 generative design center at utaustin
Name _________________________
[i] The rocket wants to move in
the direction shown. Which
direction should the rocket be
fired?
[a]
[b]
[1]
rocket in space & far from any other object
[ii] In terms of causing movement this process is most like
[a] throwing a watermelon off the back of a canoe
[b] an oil refinery burning off excess natural gas
[c] bouncing on a trampoline
[d] blowing pieces of paper off a desk
[iii]
Briefly explain your answer to [ii]
[2]
A rocket is moving in
the direction shown.
Later it is observed
moving horizontally.
In which direction(s)
must the rocket have
been pushed.
[a]
[b]
[c] both
[d] none of these
&
[3]
A rocket is stopped. Later it is stopped in
another location. Which of the following
pushes could have happened?
[a] no pushes
[b] zero TOTAL (net) pushes
[c]
[d] b&c
[e] none of these
[4]
A rocket is moving at a constant speed in the direction
shown. Later it is moving the same direction &
speed. Which of the following pushes could have
happened?
[a] no pushes
[b] zero TOTAL (net) pushes
[c]
[d] a, b &c
[e] none of these
[5]
The rockets on Rocket Randi’s sled fire for
one second at a time. To move at an average
speed of 20 cm/sec Randi fires the rockets
about one time every three seconds. Randi
then gets the sled to move at 40 cm/sec on
the same surface. To stay at this new speed,
Randi would have to fire the rockets:
[a] about one time every three seconds
[b] close to two times every three seconds
[c] more than two times every three seconds
[d] between one and two times every three
seconds
[e] none of these
[6]
Rocket Randi’s sled is observed to be moving
to the right. Circle all responses that could be
true at the moment the observation is made:
[a] The net force on the sled is zero.
[b] The net force on the sled is to the right.
[c] The net force on the sled is to the left.
[d] The momentum (inertia) is to the right
Key for Introductory Questions
[1] (a) Watermelon off canoe – We push on melon, melon pushes back [what
is mean by “equal and opposite” phrase] causing canoe to move (Gas fired
from rocket is like watermelon being thrown; Like releasing an inflated
balloon).
May want to discussion [1] prior to activity. Others can be discussed at
greater length during/after activity.
[2] (a) need to cancel upward part so only (a) “MUST” be the case. Yes, (c)
would work but the horizontal push is NOT required.
[3] (d) b and c if located in a new position.
[4] (d) a, b & c
[5] (a) Force needed is same for any constant velocity (not including air
resistance … the speeds given are relatively slow so air resistance should
be very small).
[6] All four responses are correct. On tests “inertia” has a meaning similar to
what we call “motion”.
Extension
ACCELERATION
[1] Acceleration (change in How Fast) Graphs –
Press Start Over, move the donut to the middle
of the screen (click and drag to move). Wait for
count-down (or click white square).
[2] Press Go to start the simulation. Then press N/S/E/W
buttons a number of times. Press Go again Pause.
[3] Move Force slider to 1.5 and repeat [2].
[4] Move slider to 0.5 and repeat [2].
[5] Return slider to 1.0
(a)
For Newton, a NET FORCE (imbalanced force) causes a CHANGE IN MOTION (change in
velocity) or ACCELERATION. In the simulation every time you press the N/S/E/W buttons
you apply a NET FORCE. When you do this, what happens to the acceleration graph?
(ii) Which
results in
a change
in motion
(ii) An
accler
ation
(b) How can you tell from just looking at the acceleration graph which button you pressed? (be
sure to mention color and direction +/-)
(i) A Net
N:
S:
W:
E:
Force
causes
[6] For Newton, a NET FORCE (imbalanced force
or Net Force ≠ 0) causes a CHANGE IN MOTION
(change in velocity) or ACCELERATION.
(a) How can you tell from just looking at the acceleration graph which
button you pressed? (be sure to mention color and direction +/-)
N:
S:
(ii) Which
results in a
W:
change in
motion
E:
(b) Using this SUMMARY, consider your answers to these questions.
For each scenario write if there is a non-zero NET force (Hint: Is there a
change in motion?):
(ii) An
acceleration
(i) A Net Force
(≠ 0) N causes
Net Force (≠ 0) ? (Y/)N)
How do you know?
Net Force (≠ 0) ? (Y/)N)
How do you know?
Net Force (≠ 0) ? (Y/)N)
How do you know?
Assessment
TWO RELATED ITEMS
Name: _______________________
Class Period: __________
1.
2.
A child jumps on a trampoline, as
shown above. Which of the
following causes the child to rise in
the air.
A
Inertia
B
Mass
C
A reaction force
D
A gravitational force
This question may have more than one
correct answer. Select all correct
responses.
An elevator is moving upward. Which
of the following statements could be true:
A There is a net Force downward on
the elevator.
B There is a net Force upward on the
elevator.
C The net Force on the elevator is 0
Newtons.
D The elevator has no weight.
ANSWER KEY
1.
2.
Illustrate with
Newtonia – All
3 scenarios
could be true
TAKS
Item
A child jumps on a trampoline, as
shown above. Which of the
following causes the child to rise in
the air.
A
B
C
D
Inertia
Motion
a better
word for
“Inertia”
Set
gravity
to
1
This question may have more than one
correct answer. Select all correct
responses.
An elevator is moving upward. Which
of the following statements could be true:
Moving upward but Net Force down (gravity winning)
A There is a net Force downward on
the elevator.
Mass
B There is a net Force upward on the
Applied force equal to OR greater than
elevator.
gravity (Net Force ≥ 0).
Unfortunately this
A reaction force
C The net Force on the elevator is 0
is an “action –
Applied force equal to gravity (Net
Newtons.
Force = 0).
reaction” question
A gravitational force(see watermelon
D The elevator has no weight
response in intro)
With gravitation, if an object has
mass it DOES have weight