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Physical Science Physics March 20- April 26 • • • • • 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 • • • • 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 • • • • 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 • • • • • • 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 ) • Reading – – – – • 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 • Homework – – • Facts, knowledge & concept development Word problems - theoretical application Labs - Hands on application Mechanics - Study of Motion • 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 • A dimension is a measurable characteristic – In simple terms, the dimension is the "thing" being measured • Units allow us to give it an amount. – A unit is an agreed upon standard of how to measure the dimension. • Example: a kilometer is a unit of the dimension distance • Three fundamental dimensions are: – Mass Length Time • 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? – a = ΔV/Δt = V-final - V-initial /Δt = (60 miles/hour - 0 mile/hour)/4 minutes = 15 miles/hour/min Relative Motion • Why is all motion relative? • What is absolute motion? • 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 • See physics classroom web site: http://www.physicsclassroom.com/Class/newtlaws/ • 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. • Pressure is Force/Area – It can be thought of as the amount of concentration of force • Two major categories of forces – A contact force is a force that requires physical contact between object for it to be felt. • 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. • 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 • • • 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. • 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. • 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 • • • • • 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: • 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. • Net or Resultant vector is drawn from the origin to the head of the last vector. • Magnitude can be estimate by the length of the resultant vector based upon the scale. • Mathematical • Pythagorean theorem is used for magnitude: • – 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 • • 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 • • • • 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 • • 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. • • • 2. Use Ohms' law (I = V/R) last to calculate resistance for each combination • 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) • • • • • Lab 4 - 7. Energy transformations - Solar Energy to Electricity • • • • • • 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 • Analysis of Data: Vi of carVf of carAcceleration of Car = Vf - Vi/Δt • Force to Move CarF = ma Energy and WorkE = W = F∙d Conclusions