Transcript PPT - Hss-1.us

Physical Science
Physics March 20- April 26
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Parts 14 -17 Intro to Physics Motion (March 20, 22, 27 & 29)
ABeka Chap 12 Se 12.1 Pages 307 - 313
Apologia Module #1 Pages 8 - 17 and
Module #9 Pages 203 - 228.
Dr V's Handout Secs 11 – 12 Grade 7 - 9 Topics in Physics Sciences
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Parts 18-21 Intro to Physics Newton Laws (April 3, 5, 17, & 19)
ABeka Chap 12 Sec 12.2 pages 314 - 320
Apologia Module #10 Pages 229 - 254.
Dr V's Handout Secs 11 – 12 Grade 7 - 9 Topics in Physics Sciences
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Parts 22 and 23 Parts 18-21 Intro to Physics Gravity (April 24 & 26)
ABeka Chap 12 Sec 12.2 pages 320 - 325
Apologia Module 11 Pages 255 - 284.
Dr V's Handout Secs 11 – 12 Grade 7 - 9 Topics in Physics Sciences
(An Aside) Adiabatic and Pseudo Adiabatic Process
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Diagram the adiabatic and Pseudo-adiabatic process with wind flowing over a mountain.
There are three temperature lapse rates:
Average temperature lapse rate of a decrease of 3.5°F (2°C) per 1,000 feet (304 m) of altitude.
Dry adiabatic lapse rate of a decrease of 5.5°F (3°C) per 1,000 feet (304 m) of altitude.
Moist (or saturated) adiabatic lapse rate of 3.0°F (1.5°C) per 1,000 feet (304 m) of altitude.
Assume dewpoint is constant but can never drop below the temperature .
Physics Overview
• Physics is the most basic science
– Branch of science concerned with the nature and
properties of matter and energy. The subject
matter of physics, includes motion-mechanics,
heat, light and other radiation, sound, electricity,
magnetism, and the structure of atoms (overlaps
with chemistry).
– Mechanics Study of Motion and Forces
• Kinematics - study of motion without consideration of
the forces that cause it
• Dynamics - study forces the cause of motion
• Statics - study of forces in balance - not in motion
• Classic, versus Relativistic versus quantum physics
• Relationship with Mathematics
– Physics highly mathematical
• Math pushes physics forward makes physics
useful
Mechanics - Study of Motion
Parts 14 and 15 Intro to Physics - Motion
(Kinematics - Motion without knowing
cause )
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Reading
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ABeka Chap 12 Se 12.1 Pages 307 - 313
Apologia Module #1 Pages 8 - 17 and
Module #9 Pages 203 - 228.
Dr V's Handout Secs 11 – 12 Grade 7 - 9
Topics in Physics Sciences
Videos
– Motion diagrams
http://www.youtube.com/watch?v=afvWN3qUzjc&feature=related
– Velocity vs. acceleration
http://www.youtube.com/watch?v=f3xeOA6MMDc&feature=related
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Homework
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Facts, knowledge & concept development
Word problems - theoretical application
Labs - Hands on application
Mechanics - Study of Motion
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Motion Math Relationships
– Speed: v = Δ distance/Δ time Δd/Δt
• Δ = finial - initial
• Unit: mi/h, km/h, m/s
– Velocity: Speed + direction
– Vector and Scalar Quantities
• Vector has magnitude & direction
• Scalar has magnitude only
– Acceleration: Δ velocity/ Δ Time =
a= ΔV/Δt = Δd/Δt2
– Acceleration due to gravity
• Free fall rates on earth = 9.8 m/s2
or 32 ft/s2
Speed & Velocity Vector and Scalar Quantities
Acceleration
Dimensions and Units Review
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A dimension is a measurable characteristic
– In simple terms, the dimension is the "thing" being measured
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Units allow us to give it an amount.
– A unit is an agreed upon standard of how to measure the dimension.
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Example: a kilometer is a unit of the dimension distance
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Three fundamental dimensions are:
– Mass Length Time
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Three corresponding fundamental SI units for each dimension are:
– Kilogram, Meter, Second
• Derived dimensions are a combination of different dimensions, such
as speed is a distance divided by a time.
• Composite dimensions are combinations of the same dimension,
such as area is a distance times a distance.
Velocity and Acceleration Problems
• A car is travels 80 miles in 2 hours to the west. What
is its speed and velocity?
– speed =
– velocity =
• A car goes east from 0 to 60 miles/hour in 4
minutes.
– What was its velocity after 4 minutes?
• (60 miles/hour)/2 = 30 miles/hour
– What was its average acceleration per minute (miles per
hour per minute) over the 4 minutes?
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a = ΔV/Δt = V-final - V-initial /Δt
= (60 miles/hour - 0 mile/hour)/4 minutes
= 15 miles/hour/min
Relative Motion
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Why is all motion relative?
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What is absolute motion?
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Relative Motion Problems
– Two cars (Car A and Car B)
are approaching each other.
They are now 100 miles
apart. Car A is going east at
60 mph. Car B is going west
at 40 mph. How long will it
take the two cars to reach
each other?
– Example of two cars going in
the same direction at
different speeds
– Example of motion on a
moving object
Distance Equation
• Compete Equation for Total Distance
Traveled
– d = do + Vt + ½ at2
d = total distance traveled
displacement distance
v = average velocity
t = time
do = starting
a = average acceleration
• Common Special Cases
– do = 0 (no starting displacement distance)
• d = vt + ½ at2
– do = 0 and a = 0 (no acceleration)
• d = vt
– do = 0 and v = 0 (no acceleration)
• d = ½ at2
Distance Equation
Examples
• d = do + Vt + ½ at2
Find d if do = 20m
v = 20 m/s
a = 2m/s2
t = 5 minutes
• d = do + Vt + ½ at2
– Convert t to second: 5 min = 5 min (60sec/min) = 300 sec
= 20 m +(20m/s)(300 s) +1/2(2m/s2)(300 s)2
= 20 m + 6000m + 90,000m
= 96320 m
Forces and Newton
Laws
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See physics classroom web site:
http://www.physicsclassroom.com/Class/newtlaws/
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A force is anything that can exert a push or pull on another object. A
force has the ability to change the state of motion of an object.
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Pressure is Force/Area
– It can be thought of as the amount of concentration of force
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Two major categories of forces
– A contact force is a force that requires physical contact between
object for it to be felt.
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Friction is a good example.
– An action at a distance force can exert its influence without any contact or
touching.
• Examples are gravity, magnetic and electrical forces.
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View Video on Newton's Laws
– Newton's Laws of Motion
• http://www.youtube.com/watch?v=iH48Lc7wq0U
Start here 4/3
Isaac Newton's Laws
AB Page 314 - 324
• Newton's First Law: Law of inertia (AB 314-316)
– An object not change its state of motion (moving or at rest)
until a force is applied to it.
• Newton's Second Law: F = m x a AB 316 - 318
– The acceleration of an object depends directly upon the net force acting upon
the object, and inversely upon the mass of the object.
• Newton's Third Law: Law of reciprocal actions
AB 316 - 318
– "To every action force there is an equal, but opposite, reaction force".
A more direct translation is: To every action there is always opposed
an equal reaction.
Newton 3rd Law and Rockets
Momentum
Intro to Momentum pages 319-320 A Beka and:
http://www.youtube.com/watch?v=XFhntPxow0U&feature=fvwrel
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Momentum = mass • velocity (Momentum is a vector quantity)
In physics, the symbol for the quantity momentum is the lower case "p".
Thus, the above equation can be rewritten as
p=m•v
– where m is the mass and v is the velocity. The equation illustrates that
momentum is directly proportional to an object's mass and directly proportional to
the object's velocity.
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The units for momentum would be mass units times velocity units.
– The standard metric unit of momentum is the kg•m/s.
– There are a variety of other units that are acceptable (though not conventional)
units of momentum.
• Examples include kg•mi/hr, kg•km/hr, and g•cm/s. In each of these examples, a mass
unit is multiplied by a velocity unit to provide a momentum unit. This is consistent with
the equation for momentum.
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Momentum Conserves meaning as stated in the "Law of Conservation of
Momentum):
– p1 = p2 or
m1v1 = m2v2
For more help go to: http://www.physicsclassroom.com/Class/momentum/
Momentum Problems Examples
• In an elastic frictionless collision the total momentum
before and after the collision must be equal as below
– Elastic collision means there is no tendency of objects to stick together
– Non-elastic collision means the objects completely stick together
– Actual collisions are a combination of both types
See http://www.bojensen.net/Exp/elastic.htm
Friction
• Friction the force of two surfaces in contact.
– It is not a fundamental force,
– It is derived from the electromagnetic forces between atoms specifically electrons.
– When contacting surfaces move relative to each other, the
friction between the two objects converts kinetic energy into
thermal energy, or heat.
– Friction between solid objects is often referred to as Dry Friction
– Frictional forces between two fluids (gases or liquids) as called
Fluid Friction which is related to its viscosity.
– In addition to these there is also Internal Friction which illustrates
a body's ability to recover from external deformation.
• Friction always opposes motion opposite the direction of
motion
Static and Kinetic Friction (244):
• Static friction: Static friction occurs when the two
objects are not moving relative to each other (like a rock
on a table).
– The initial force to get an object moving is often
dominated by static friction. The static friction is in
most cases higher than the kinetic friction.
• Kinetic friction: Kinetic (or dynamic) friction occurs
when two objects are moving relative to each other and
rub together (like a sled on the ground). The coefficient
of kinetic friction is usually less than the coefficient of
static friction. Types of Kinetic Friction are:
– Sliding and Rolling friction
Force and Circular Motion
(p 260 Apologia not in ABeka)
• Centripetal force - in towards center - real
• Centrifugal force - out from center - apparent
• Equal and opposite. Both equal to V2/r
Centripetal and Centrifugal Force
Examples Hurricane
• Given the eye of an Hurricane is 40 km across and
the velocity is 100 knots calculate Centripetal and
Centrifugal Force Pair in Newtons for 1 Kg of air.
– First must convert to MKS
• 40 km = 1000 m/km (40 km) = 40,000 m, so r = 20,000 m
• 1 knot = 0.514 meters / second
• 100 knots = 0.514 m/s/knot (100 knots) = 51.4 m/s
– Now use Cent. F = V2/r = (51.4 m/s)2 /(20,000 m)
= 2641.96m2/s2/ (20,000 m)
= 0.13 Nt
Centripetal and Centrifugal Force
Examples Tornado
• Given a Tornado is 2 km across and the velocity is
200 knots calculate the Centripetal and Centrifugal
Force Pair in Newtons for 1 Kg of air.
– First must convert to MKS
• 2 km = 1000 m/km (2 km) = 2,000 m, so r = 1,000 m
• 1 knot = 0.514 meters / second
• 200 knots = 0.514 m/s/knot (200 knots) = 110.8 m/s
– Now use Cent. F = V2/r = (110.8 m/s)2 /(1,000 m)
= 12276.64m2/s2/ (1,000 m)
= 12.28 Nt
Or 94.4 times stronger than for the hurricane!
Graphic and Mathematical
Videos: Vectors Graphically
Vectors
Vectors Algebraically
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Graphic representation
Vectors have both magnitude
and direction
Vectors can be represented
both graphically and
mathematically.
Vectors have there own rules
for addition and multiplication
different from scalars.
Graphically they are
represented by arrows
Mathematically they can be
represented by trigonometric
relationships with arrow or bar
over vector symbol or bold.
Ex
V or V or V
Note that ½ power means "square root"
Mathematical Representation
Magnitude of Vector = (a2 +b2)1/2
Dir of Vector = Tan-1(b/a)
17.32 mi
Ex. V = (17.322 mi+102 mi)1/2 = 20mi
Dir = Tan-1(17.32/10) = 60˚
10 mi
Graphic and Mathematical Vector
Addition
Pages 309-311 in Abeka
Graphical:
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Graphical vector additions
involves the use the vector
arrows drawn to an exact
scale and orientation so that
tail of one vector (V1)starts at
the origin and the tail of the
next vector (V2) is drawn
from the head of the first
vector.
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Net or Resultant vector is
drawn from the origin to the
head of the last vector.
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Magnitude can be estimate
by the length of the resultant
vector based upon the scale.
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Mathematical
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Pythagorean theorem is
used for magnitude:
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V1
V2
V12 + V22 = R2
R = (V12+V22)1/2
Direction = Tan -1 (V1/ V2)
For more help on vectors go to
http://www.physicsclassroom.com/Class/vectors/U3l1b.cfm
Free-Body Diagrams
• A free-body diagram is a special
example of the vector diagrams
• Free-body diagrams show the
relative magnitude and direction of
all forces acting upon an object
• Size of the arrow in a free-body
diagram reflects the magnitude of
the force.
• Direction of the arrow shows the
direction that the force is acting.
• Each force arrow in the diagram is
labeled to indicate the exact type of
force.
Free-Body Diagram
Example
• Draw a free-body diagram for a book at
rest on a tabletop.
Determining the Net Force
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The existence of an
unbalanced force for a given
situation can be quickly
realized by looking at the
free-body diagram or
vectors for that situation.
If the force vectors do not
add up to zero then there is
a net or resultant force.
Fnet = 400 N
F
F
Using Newton's Second Law
F = ma to Solve Problems
• F = ma
F
10 N
50 N
a = F/m
m
5kg
20Kg
m = F/a
a
25m/s2
6m/s2
Using Newton's Second Law
F = ma
• F = ma
F
10 N
50 N
120N
a = F/m
m
5Kg
2Kg
20Kg
m = F/a
a
50m/s2
25m/s2
6m/s2
Energy and Work
• Energy is the ability to do Work (Joules)
– Work = F x distance
– Energy and Work have the same units
• Kinetic energy is energy because of an objects motion
KE = 1/2mv2
• Potential energy is energy because of an objects
position PE =ρgh
• Energy can neither be created or destroyed only change
forms
– Energy transform examples
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Light to heat
Sound to heat
Heat to sound
Mechanical to electrical
• Power is the rate of energy production or use:
– Power = Energy/time = Joules/sec = Watt
See http://www.physicsclassroom.com/Class/energy/
Relationship Between Temperature
and Heat
• Temperature is the measure of the
average KE
• Heat is the Measure of the total energy
(KE and PE)
– Heat is also used to describe the transfer of
thermal energy
Four Fundamental Forces
AB p 325
Videos: basic: http://www.youtube.com/watch?v=FEF6PxWOvsk
advanced: http://www.youtube.com/watch?v=p5QXZ0__8VU
• Strong nuclear - Act over very short distance and keep
protons
and neutrons in the nucleus together.
• Weak nuclear - allows radioactive decay (radioactivity such
as xrays).
• Electromagnetic - responsible for electrical and magnetic
forces.
• Gravity - very weak but can act activity long ranges, God's
mechanism for keeping the universe together
– Gravity general law F = Gm1m2/d2 relation to F = ma
– Video Newton's (Classic) versus Einstein's Relativistic Gravity
– http://www.youtube.com/watch?v=O-p8yZYxNGc
– http://www.youtube.com/watch?v=8acTvtzMGCE&feature=related
Newton's Universal Law of
Gravitation
Mass and Distance Effect on
Gravity
Example 1
• Determine the force of gravitational attraction between
the earth (m = 5.98 x 1024 kg) and a 70-kg physics
student if the student is standing at sea level, a distance
of 6.38 x 106 m from earth's center.
– The solution of the problem involves substituting known values of G
(6.673 x 10-11 N m2/kg2), m1 (5.98 x 1024 kg), m2 (70 kg) and d (6.38 x
106 m) into the universal gravitation equation and solving for Fgrav. The
solution is as follows:
Example 2
• Determine the force of gravitational attraction between
the earth (m = 5.98 x 1024 kg) and a 70-kg physics
student if the student is in an airplane at 40000 feet
above earth's surface. This would place the student a
distance of 6.39 x 106 m from earth's center.
– The solution of the problem involves substituting known values of G
(6.673 x 10-11 N m2/kg2), m1 (5.98 x 1024 kg), m2 (70 kg) and d (6.39 x
106 m) into the universal gravitation equation and solving for Fgrav. The
solution is as follows:
Preparation for the Lab
1. Review Steps of the Scientific Method
Step 1: Make initial observations of the world around you. In this way you are able to
define a problem or question. Sometimes you may use the observations of others
during this step. For example, you observe the sky conditions for a month and you
notice that there seems to be two types of basic cloud forms, cumuliform (puffy) and
stratiform (layered).
Step 2: You then propose a hypothesis to explain observations. Your hypothesis
needs to be testable, so you can determine if it is true or not. For example, you think
about your observations and you propose that the types of clouds, cumuliform or
stratiform, are related to how fast the temperature cools off with height. So you state
that for cumulus clouds to form the air needs to cool at least by 4 F for every 1000
feet in elevation.
Step 3: Test the hypothesis with further observations or experiments. You gather
data, temperature information from weather balloons (rawinsondes), and you record
the types of clouds that form along with how fast the temperature cools.
Step 4: Analyze data from observations or experiments. You then plot the
temperature and cloud data on a diagram and see if your hypothesis or prediction is
correct.
Step 5: State your conclusions about the hypothesis based upon your data
analysis. If your conclusions show that the hypothesis is correct, you may want to do
further experiments to make sure that your hypothesis is always true, or ask new
questions that expand upon the knowledge gained. If it proved to be false, then you
need to go back to step 1 and re-examine the observations in order to make a new
hypothesis.
Hypotheses, Theories, and Laws
Hypotheses: An initial explanation of an observation
Theories: Workable hypothesis for body of data/observations - able to make prediction
Laws: Description of behavior - doesn't mean that it is correct all the time.
Lab 4 - 6. Magnetism
• All electric currents produce
magnetic fields
• All Magnetic are produced
by electric current
• 1. Using the provide
magnets and iron filings
identify the north and south
pole of each magnet.
• 2. Draw diagram of the
magnetic files and relate to
electricity and EM force.
Station 2 * Lab 4 - 5 Ohms' Law - Electrical Current
Relationships
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Instructions: (make a hypothesis of which bulb will use less energy)
1. Record measurements of Wattage, Voltage and Current using the Kill-a-Watt®
device for lights.
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2. Use Ohms' law (I = V/R) last to calculate resistance for each combination
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3. Given that it costs $0.15 per KW-HR, calculate how much it cost to run the
incandescent versus, CFL versus LED bulbs for a 100 hours.
100 watt Incandescent = 25 watt CFL = 10 watt LED
Cost to run a 100 Watt Incandescent Bulb for 100 hours: 100 W x 0.15 = $15
Equivalent CFLs use 25% X $15 = $3.75 (savings of $11.25 from Incandescent)
Equivalent LEDs use 10% X $15 $1.50 (savings of $13.50 from Incandescent)
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Lab 4 - 7. Energy transformations - Solar
Energy to Electricity
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1. Determine the mass of the car. ~136.7 g
2. Run the two solar power cars over a measure track
3. Measure the time it took to travel that distance
4. Calculate the work performed and the energy needed to perform that
work.
5. List and describe as many of the energy transformation you can think of
as the energy is transformed from inside the Sun to making the car move.
Data Collected:
Mass of Car (Kg)Distance of Track (d)Time Car took to travel d~136.7 g
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Analysis of Data:
Vi of carVf of carAcceleration of Car = Vf - Vi/Δt
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Force to Move CarF = ma
Energy and WorkE = W = F∙d
Conclusions