Transcript 2 - ScienceScene

Dr. M. H. Suckley & Mr. P. A. Klozik
Email: [email protected]
Additional copies of the Conference Handout may be Obtained at:
http://www.ScienceScene.com
(The MAPs Co.)
Motion
A Teacher Designed Unit Based Upon the Michigan Benchmarks
I. Introduction
4
II. Michigan Benchmarks
4
III. Unit Objectives
5
IV. Prerequisite Skills and Formative Evaluation
5
V. Instructional Unit
6
VI. Summative Evaluation
21
II. Michigan Benchmarks for Motion
Prerequisit
e
Skill
force
s
V=d/
t
F=mx
a
Futur
e
Unit
11
1. Describe or compare motions of common objects in terms of
speed and direction.
2. Describe how forces (pushes or pulls) are needed to speed up,
Key
concepts:
Words--east,
north, south,
right, left,
up,
slow
down, stop,
or changewest,
the direction
of a moving
object.
down. Speed words--fast, slow, faster, slower.
3. Key
Qualitative
describe
andincompare
motion in two
concepts:
Changes
motion--speeding
up, dimensions.
slowing down,
Real- world
contexts:
Motions ofpull,
familiar
objects
in two
turning.
Common
forces--push,
friction,
gravity.
Size
of in
4. Key
Relate
motion
of
objects
to
unbalanced
and
balanced
forces
concepts:
Twodimensional
motion--up,
down,
curved
path.
dimensions,
including
rolling or
change
is related
to strength
of thrown
push orballs,
pull. wheeled vehicles,
two
dimensions.
Speed,
direction, change in speed, change in direction.
sliding objects.
5.
Design
strategies
forPlaying
moving
objects
by application
of forces,
including
Realworld
contexts:
ball,
moving
chairs,
sliding
objects.
Key
concepts:
Changes
in
motion
and
common
forces--speeding
Realworld
contexts:
Objects
in
motion,
such
as
thrown
balls,
the
use
of simple
machines.
up,
slowing
down,
pull, friction, gravity, magnets.
roller coasters, carsturning,
on hills,push,
airplanes.
Constant motion and balanced forces. Additional forces-Realworld contexts:
Changing
direction--changing
direction of a
attraction,
repulsion,
action/ the
reaction
pair (interactionthe
force),
billiard
ball,
bus turning
corner;ischanging
speed--car
speeding up,
buoyant
force.
Size of a
change
related tothe
strength
of
a unbalanced
rolling ball slowing
down,
magnets
changing the motion of objects,
force and
mass
of object.
walking, swimming, jumping, rocket motion, objects resting on a table,
tug-world
of- war.
Realcontexts: Changing the direction--changing the direction
of a billiard ball, bus turning a corner; changing the speed--car
speeding up, a rolling ball slowing down, magnets changing the
motion of objects, walking, swimming, jumping, rocket motion,
objects resting on a table, tug- of- war.
III. Unit Objectives for Motion
1. Given the following list of terms, identify each term's correct definition.
Conversely, given the definition, identify the correct term.
acceleration, constant acceleration, force, inertia, kinetic energy, linear motion,
mass, momentum, speed, time, velocity, weight,
2. Describe how forces (pushes or pulls) are needed to speed up, slow down, stop,
or change the direction of a moving object by:
3. Describe and compare motion in two dimensions. Given the distance (x), the
time (t) and the formula v = x / t, calculate the speed (v) of any object moving in a
straight line with constant velocity. (Newton's First Law)
4. Relate motion of objects to unbalanced forces in two dimensions. (Newton’s
Second Law)
a. Given the formula f = m x a, calculate the force acting on an
object with a mass (m), moving with a constant acceleration (a).
b. Given the formula a = (vfinal - vinitial) / time, compute the acceleration
of an object moving in a straight line with constant acceleration.
5. Relate motion of objects to balanced forces in two dimensions. Given an object
at rest or in motion identify the forces acting on the object. (Newton's third Law of
Motion.)
5
IV. Prerequisite Skills (skills learners must posses to be successful)
1. Linear measurement skills
2. Use of a stopwatch
3. Computational skills
4. Recording data
5. Cooperative work skills
6. Verbal Skills
7. Communication
8. Reading comprehension
8
Formative Evaluation
(Determining if the learner is being successful along the way)
Observation of group interaction
Instructor questions directed to individual students
Ongoing review of data obtained though experimentation
Summative Evaluation
(Determining How Successful the Learner has been Mastering the Unit)
Laboratory Report
Comprehensive exam
essay
forced answer (multiple choice, fill in the blank)
2
V. Instructional Unit
A. Forces
1. Finding the Forces
2. Types of Force
6
10
B. Motion in two dimensions – (Newton’s 1st )
1. Observing Motion
2. Inertia - Fundamentals
12
13
14
C. Motion - unbalanced forces in two dimensions (Newton’s 2nd)
1. Observing Acceleration
2. The affect of Mass on Acceleration
15
16
17
D. Motion - balanced forces in two dimensions (Newton’s 3rd )
1. Equal and Opposite
2. Equal and Opposite another Look20
18
19
20
Finding The Forces Activities
1. Have someone hold a 500-gram hooked mass (HM) in their
outstretched hand. Use the arrows so indicate all the forces
acting on the HM.
2. Hang the hooked mass from a rubber band. Use the arrows
to indicate the forces acting on the HM.
3. Hang the hooked mass from a string. Release the string to
drop the HM. (Please catch it.’)
4. Place the HM on a platform spring scale.
5. Place the hooked mass on a soft sponge or piece of foam rubber. The sponge
should be soft and about the size of the HM. Push the HM with a horizontal force.
The force you apply should be large enough to affect the sponge, but not so large
as to make the sponge or the HM slide.
6. Place a coin at the edge of the table. Give it a flick with your finger so it hits the
floor some distance away. Make a free-body diagram showing the forces acting
on the coin (1) setting on the table, (2) while your finger is in the process of
flicking it and (3) while it is moving through the air.
7. Out of a 3 x 5 card, make a device that allows you to flick one coin at the same
time that you simply drop a second coin.
6
Finding The Forces Activities
2.
7.
1.
1.
6.
3.
2. 3.
4.
4.
5.
6.
5.
8
7.
Finding The Forces
1. At Rest
5. At Rest
7
2. At Rest
3. Acceleration
6. At Rest and Accelerating
4. At Rest
7. Accelerating
Types of Forces
A force is defined as any push or pull that results in accelerating motion
Circular - When objects move in circles, a force acts with a direction that is toward the
center of the circle. We call this direction CENTRIPETAL
Circular
Gravitational - All objects attract all other objects with a force called gravitational force.
Electromagnetic - Electric forces act on objects when the object carries a net electric
Gravitational
charge or a non-uniform distribution of charge. Magnetic force is also observed
around a moving electric charge and act on those charges. Physicists believe that all
magnetic forces are produced by moving charges.
Electromagnetic
Frictional - Frictional forces are often classified as sliding, rolling, static and fluid.
Sliding and rolling frictional forces result when solids in contact pass by each other.
Static frictional force results when solids are in contact, at rest and when a force or
forces are trying to cause them to move with respect to each other. Fluid frictional
force results when a solid is moving through a gas or a liquid.
Frictional
Normal
Normal - “Normal” means “perpendicular
to”. Whenever an object is placed on a
surface, a force acts normal to the surfaces in contact. This causes the supporting
surface to sag. Since this sagging is slight, it often goes unnoticed. However, it is
always there and the resulting force of the surface attempting to return to its original
position is perpendicular to the surface.
Tension
Tension - Tension force is the force exerted by a string, spring, beam or other object
which is being stretched compressed. The electric forces among the molecules give
rise to the force.
7
Newton’s First Law
An object stays at rest or continues to
move in a straight line at a constant
speed unless acted on by a force.
V=d/t
Time
Observing Motion
Distance
t0
t1
.50-meters
Finish Point
Starting
Point
Trial 1
Sec.
Trial 2
Sec.
Trial 3
Sec.
Average
Sec.
Distance
meters
Velocity
Meters/sec
V=d/t
0.43
0.44
0.43
0.44
.500
1.14
0.31
0.32
0.32
0.32
.350
1.09
Equipment Set-Up
6
Jump
2
1
0
Time
• The interval between two events.
00 03
00 25
00
S
T
A
R
T
1
S
T
O
P
0
Distance
• The interval between two objects.
S
T
A
R
T
S
T
O
P
0
Inertia
Jump
2
Applying Small Force
Applying Large Force
What is Inertia?
Answer:
The tendency of matter to remain at rest if it
is at rest or, if moving, the tendency to keep
moving in the same direction unless acted
upon by some outside force.
0
2
Newton’s Second Law
When a force acts on a moving object, it will
accelerate in the direction of the force dependent
on its mass and the force.
F=mxa
Observing Acceleration - of a Toy Car
.500-meter
.350-meter
.150-meter
t2
t0
t1
B
A
0.350-m
t0→ t1
0.500-m
t0→ t2
0.150-m
t1→ t2 (t2- t1)
First time trial
0.32
0.43
0.11
Second time trial
0.31
0.44
0.13
Third time trial
0.32
0.43
0.11
(4) Average Time
0.32
0.44
0.12
(5) Average velocity v = d / t
6) Time (when average velocity occurred)
V1 (.350/.32)
1.09-m/s
V2 (.150/.12)
1.25-m/s
Position A
TA = (t1 + t0) /2
0.16-sec
Position B
TB = (t2 + t1) / 2
0.38-sec
(6) v = change in adjacent velocity
v= v2 – v1
0.16-m/s
(7) T = change in time between adjacent velocity
t = TB – TA
0.22-sec
(8) a = acceleration between points
a = v / t
13
Starting Point
.73-m/s/s
.73-m/s2
The Affect of Mass on Acceleration
8
Battery
Trial 1
Sec.
Trial 2
Sec.
Trial 3
Sec.
Average
Sec.
Distance
meters
Velocity
Meters/sec
Without
0.43
0.44
0.43
0.44
.500
1.14
With
0.31
0.32
0.32
0.32
.500
1.09
Newton’s Third Law
Every Action Has An Equal
And
Opposite Reaction.
f1 = f 2
Newton’s Third Law
Equal and Opposite
Slippery
Plastic
1. Crumple the plastic until it looks very wrinkled
2. Place the slippery plastic on a solid, flat surface.
3. Place the car on top on the slippery plastic.
4. Start the car and observe the car and the slippery plastic.
4
Equal and Opposite, Another Look
1. Place two soda cans on a flat surface approximately 25-cm apart.
2. Place the plastic on top of the soda cans.
3. Place the car on top on the plastic as shown.
4. Start the car and carefully observe the car and the plastic.
3
Summative Evaluation
The Class Debriefing - Did we Get There?
If we did
1. The Laboratory Report
2. The Exam
3, Celebration
If we did not
1. Re-teach
2. Provide alternate activities
3. Retest
The Stopwatch
We Had A Great Time