Download Presentation - ScienceScene

Dr. M. H. Suckley & Mr. P. A. Klozik
Email: [email protected]
http://www.ScienceScene.com
(The MAPs Co.)
Motion
I. Introduction
II. Newton’s First Law
III. Newton’s Second Law
IV. Newton’s Third Law
Motion
I. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . 3
II. Newton’s First Law . . . . . . . . . . . . . . . . . . . . 4
A. Motion
..... 6
2. Observing Motion of a Toy Car. . . . . . . . . . . . . . 5
1. Measuring the Velocity of Various Objects
B. Inertia
....................... 9
2. Using Your Marbles . . . . . . . . . . . . . . . . . . . 10
3. FUN With Inertia . . . . . . . . . . . . . . . . . . . . . 10
1. Fundamentals
Motion
III. Newton’s Second Law . . . . . . . . . . . . . . . . . . . 11
A. Acceleration (change in velocity)
1. Observing Acceleration . . . . . . . . . . . . . . . . . . .12
2. Acceleration A More Complete Picture . . . . . . . . 13
B. Fundamentals of Force
1. Observing Forces (using the “Gizmo”) . . . . . . . . . 14
2. Finding The Forces . . . . . . . . . . . . . . . . . . . . . . 15
3. Types of Force. . . . . . . . . . . . . . . . . . . . . . . . . . 24
4. Forces in a Collision . . . . . . . . . . . . . . . . . . . . . 26
5. The Falling Cup . . . . . . . . . . . . . . . . . . . . . . . . 27
C. The Affect of Mass on Acceleration
. . . . . . 28
Motion
IV. Newton’s Third Law . . . . . . . . . . . . . . . . . 29
A. Equal and Opposite . . . . . . . . . . . . . . . . . . .30
B. Equal and Opposite Another Look . . . . . . . . . 31
C. Making Formulas Out of Words . . . . . . . . . . . . 33
We Had A Great Time
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.
1
Naïve ideas:
1. The distance an object travels and its displacement are always the
same.
2. An object’s speed and velocity are always the same.
3. An object having inertia is always at rest.
4. Acceleration is always in a straight line.
5. Acceleration means that an object is speeding up.
6. The numerical value of acceleration is always a positive number.
6
0
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
6
Starting
Point
Trial 1
Sec.
Trial 2
Sec.
Trial 3
Sec.
Average
Sec.
Distance
meters
Velocity
Meters/sec
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
0
2
1
0
Measuring The Velocity of Various Objects
Object
1. Toy Cars
Distance
Time
Speed
Average
Distance
Time
Speed
Average
Battery Powered Car
Pull Back Car
400-ml. Beaker
250-ml. Beaker
Wall Clock
Wrist Watch With Second Hand
Tennis Ball
Super Ball
Trial 1
Trial 2
Trial 3
2. Flowing
Water
Trial 1
Trial 2
Trial 3
3. Clock
Hands
Trial 1
Trial 2
4. Bouncing
Ball
Trial 1
Trial 2
Trial 3
Speed of Sound
5. Sound
Trial 1
Trial 2
Trial 2
Time
• The interval between two events.
00 03
00 25
00
S
T
A
R
T
1
S
T
O
P
Distance
• The interval between two objects.
S
T
A
R
T
S
T
O
P
Measuring the Filling Speed of Water
a. Turn the water on at a moderate rate. Keep this flow constant for both
beakers.
b. Fill the 400 ml. beaker with any amount (approximately one fourth of the
beaker) of water, while timing (t).
c. Mark the top of the water, and measure its distance in meters from the
bottom of the beaker to the top of the water.
d. Repeat this for two additional readings.
e. Compute the distance (x) the water level rose using:
x1 = L1 - L0
x2 = L2 - L1
x3 = L3 - L2
f. Compute the velocity of water flow using: v = x / t.
g. Repeat this for two additional readings.
h. Obtain average velocity of the water flow.
i. Repeat for a 250 ml beaker.
3
Measuring The Speed Of A Clocks Second Hand
a. Select a wall clock with a second hand.
b. As the tip of the second hand rotates
around the center of the clock traveling
a certain distance (x), in a given time (t).
d. Compute the distance traveled by the
outer point of the second.
e. Compute the speed using: v = x / t
ScienceScene.com
Note:
1) The tip of the second hand moves in a circle. In order to find the distance
traveled, we must find the circumference of that circle. To determine the
circumference, we must measure the radius (r) of the circle in meters. The
radius is the distance between the center of the clock, and the tip of the
second hand. Double that figure to obtain the diameter, and multiply that
result by pi (3.14).
2) The total distance traveled would be the number of full revolutions (N)
multiplied by the distance traveled or x = (N) x 2r x 3.14. Call this distance
x, and record.
Measuring The Velocity Of A Bouncing Ball.
a. The total distance (x) that the ball traveled is
equal to the sum of the heights x1, x2 and x3. The
initial height is x1, the final height is (x3) and the
average of x1 and x3 is x2. The total distance (x)
that the ball traveled is equal to the sum of the
heights (x = x1 + x2 + x2 + x3). The heights are
most easily measured by bouncing the ball near a
wall, using the brick divisions to help in the
measurement of the height of the bounce.
b. The time (t) taken for the ball to make two
bounces would be measured from the starting
point (the release point), to the end point (the top
of the second bounce).
c. Compute the average speed using: v = x / t.
d. Collect three sets of data and calculate the
average velocity.
e. Repeat for the second ball
1
Simulation
x1
x2
x2
x3
Total Distance (x) = x1 + x2 + x2 + x3
Speed Of Sound
BANG!
Observers start their stopwatches when they see the flash of light
created at the same instant a loud sound occurs. They stop their
stopwatches when they hear the sound. Using their data calculate the
speed of sound.
2
1.
2.
3.
4.
Trial
Distance
Time
1
331.2-m
1.01-sec.
2
331.2-m
1.06-sec.
3
331.2-m
1.08-sec.
Velocity
Experimental Speed of Sound = distance / time
Theoretical Speed of Sound = 330 m/sec. + (.6 m/sec. x Temperature)
Temperature = 23.1 ºC
Calculate Percent of Error
Inertia
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.
2
1
Newton's First Law - Inertia
Objects at rest remain at rest.
A lot of inertia!
Very little inertia.
Since the train is so huge, it is difficult to move the train from rest.
Since the baby carriage is so small, it is very easy to
move from rest.
Objects in motion remain in motion in a straight line (unless acted upon by an outside force).
A lot of inertia!
Very little inertia
Since the train is so huge, it is difficult to stop it once it is
moving.
Since the soccer ball is so small, it is very easy to stop it
once it is moving.
0
Inertia - Using Your Marbles
Newton’s First Law
2
4
Newton’s First Law
3
Newton’s First Law
2
Newton’s First Law
1
Click for Inertia Movie
Newton’s First Law
0
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
B
13
t0
t1
A
Starting Point
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
V1
1.09-m/s
V2
1.25-m/s
6) Time (when average velocity occurred)
Position A
TA = t1/2
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
.73-m/s/s
.73-m/s2
Acceleration – A More Complete Picture
Excel Worksheet – Push F9 to Reveal Calculations
t0
Trial #1 0.00
Trial #2 0.00
Trial #3 0.00
Av. Time (seconds)
t1
t2
t3
t4
t5
t6
t1 - t0
t2 - t1
t3 - t2
t4 - t3
t5 - t4
t6 - t5
V1=2/(t1-t0)
V2=2/(t2-t1)
V3=2/(t3-t2)
V4=2/(t4-t3)
V5=2/(t5-t4)
V6=2/(t6-t7)
T1=(t0+t1)/2 T2=(t1+t2)/2
T3=(t2+t3)/2
T4=(t3+t4)/2
T5=(t4+t5)/2
T6=(t5+t6)/2
∆T1=T2-T1
∆T2=T3-T2
∆T3=T4-T3
∆T4=T5-T4
∆T5=T6-T5
∆V1=V2-V1
∆ V2=V3-V2
∆V3=V4-V3
∆V4=V5-V4
∆ V5=V6-V5
0.00
Time to travel 2.00 Meters"
Av. Velocity for 2.00 Meters
Av. time velocity Actually occurred
∆ T = Change in time between adjacent velocity
∆V = Change in adjacent velocity
A1= ∆V1/∆T1 A2=∆V2/∆T2 A3=∆V3/∆T3 A4=∆V4/∆T4 A5=∆V5/∆T5
Acceleration = ∆V / ∆T
Observing Forces
Bubble Level
Accelerometer
Movement of the Car
None
Forward
Backward
8
Circular
Direction of FORCE (movement of the accelerometer bubble)
It remains constant
It moves forward
It moves backward
It moves towards the center of rotation
1
Circular Motion
The following diagram helps to explain the circular motion of an object. This motion
depends on the object’s inertia, straight line direction, and the force applied by a string
pulling the object towards the center of the circle.
ID
ID
ID
ID = Inertia direction
Rx = Resultant of Inertia & Center Pull
R4
CP = Center Pull direction
CP
CP
R3
CP
ID
CP
CP
ID
CP
CP
CP
R1
ID
R2
ID
3
0
ID
Understanding Forces
Types of Forces
Pushes and Pulls
ScienceScene
2
Finding The Forces Activities
Read the description in the handout and identify the Forces for each activity
7.
1.
6.
2. 3.
4.
5.
1
8
Finding The Forces Activities
1. At Rest
1.
2. At Rest
3. Acceleration
2.
3.
4. At Rest
4.
5. At Rest
7. Accelerating
6. At Rest and Accelerating
7.
6.
5.
7
0
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
Forces in a Collision
1. The diagram shows a child and an adult pushing on each other while
holding bathroom scales to measure the forces. Predict how they will
move. Explain your prediction. (Does the answer depend on who does the
pushing? What if both push at the same time?)
2. Which scale will show the biggest number?
3. Suppose the situation was slightly different than the illustration. For each
situation below, predict how the readings on the scales would compare
with each other. Explain your predictions.
a. If the adult’s chair was backed up against a wall.
b. If the child’s chair was backed up against a wall.
c. If both chairs were backed up against a wall.
The Falling Cup
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
0.56
0.57
0.60
0.58
.500
0.86
Newton’s Third Law
Every Action Has An Equal
And
Opposite Reaction.
f1 = f 2
3
Newton’s Third Law
2
Newton’s Third Law
1
Newton’s Third Law
0
Equal and Opposite - Newton’s Third Law
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
2
The Hover Cover
Balloon Powered
Materials: Scissors, Plastic lid from a cottage cheese
container, Push-pull squirt cap from a bottle
of dishwashing liquid, Glue, Round balloon
Instructions:
1. Cut a hole 3/4 inch in diameter in the center of the plastic
lid from the cottage cheese container.
2. Center the push-pull squirt cap over the hole and glue it to
the lid, with the lid's writing face up. Use enough glue so
that no air spaces are left between the plastic surface of
the cap and the plastic of the lid. Let the glue dry
completely.
3. Blow up a round balloon and slip the opening over the
opening on the closed squirt cap.
4. Place the device on a smooth surface, such as a table top,
and lift the squirt-cap opening so that the air escapes from
the balloon and your space car will glide effortlessly.
1
Newton’s Third Law
0
The Stopwatch
MAKING FORMULAS OUT OF WORDS
SPEED =
CHANGE IN DISTANCE
CHANGE IN TIME
VELOCITY = CHANGE IN DISTANCE & DIRECTION
CHANGE IN TIME
ACCELERATION =
CHANGE IN SPEED
CHANGE IN TIME
ACCELERATION =
CHANGE IN VELOCITY
CHANGE IN TIME
Δd
Δt
Note: to make the equation simple we place “
SPEED(s) =
VELOCITY(v) =
7
Δs or Δd
Δt
ACCELERATION (a) =
Δs
Δt
ACCELERATION (a) =
Δv
Δt
Δ “ in place of the word “change”
Note: The arrow indicates a change in direction
We Had A Great Time