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Transcript
OBJECTIVE 5 - Motion, Forces, and Energy Physics 1 – Introduction http://www.youtube.com/watch?list=PL005B8C98C0D8AB59&v=pE3WhJjtxh8&feature=player_detailpage *Physics units: http://www.cstephenmurray.com/onlinequizes/physics/solvingequations/physicsunits.htm *Variables 1: http://www.cstephenmurray.com/onlinequizes/physics/solvingequations/variables1.htm *Variables 2: http://www.cstephenmurray.com/onlinequizes/physics/solvingequations/variables2.htm *Choose the correct equation: http://www.cstephenmurray.com/onlinequizes/physics/solvingequations/choosinganequation.htm *Moving variables pre-lesson: http://www.cstephenmurray.com/onlinequizes/physics/solvingequations/prelessonmovingvariables.htm *Moving variables: http://www.cstephenmurray.com/onlinequizes/physics/solvingequations/movingvariables.htm Specific Heat Specific heat: Cp, heat, measured in joules (J), required to raise the temperature of one gram of a substance by 1 oC; it varies according to the substance and its state of matter; Cp of liquid water is about 4.18 J/ (goC) Example: How much heat is required to increase the temperature of 15 grams of water from 20 oC to 25 oC? Heat = mass x change in temp. x specific heat Heat = 15g x (25 oC – 20 oC) x 4.18 J/ (g oC) = 313.5 J Water phase diagram - temperature does not change during a phase change! Physics 2 – Density & Specific Heat http://www.youtube.com/watch?v=XuCul_jTOzg&list=PL005B8C98C0D8AB59&feature=player_detailpage Physics 2A – Density & Specific Heat (exercise) http://www.youtube.com/watch?list=PL005B8C98C0D8AB59&v=1yIbd2mdZ0w&feature=player_detailpage Speed, Momentum, and Acceleration Physics 4 – Motion, Velocity & Acceleration http://www.youtube.com/watch?list=PL005B8C98C0D8AB59&v=4NADtMUsp2U&feature=player_detailpage Motion: change in position over a certain amount of time. Speed: rate at which an object moves. Speed = distance/time Velocity: describes speed in a given direction. *Calculating speed 1: http://www.cstephenmurray.com/onlinequizes/physics/speedexercises/calculatingspeed1.htm *Calculating speed 2: http://www.cstephenmurray.com/onlinequizes/physics/speedexercises/calculatingspeed2.htm *Calculating speed 3: http://www.cstephenmurray.com/onlinequizes/physics/speedexercises/speed3.htm *Calculating avg. speed 1: http://www.cstephenmurray.com/onlinequizes/physics/speedexercises/averagespeed.htm *Calculating avg. speed 2: http://www.cstephenmurray.com/onlinequizes/physics/speedexercises/averagespeed2.htm Momentum: tendency of an object to keep moving in the direction in which it is moving. Momentum = mass x velocity *Understanding momentum: http://www.cstephenmurray.com/onlinequizes/physics/momentum/understandingmomentum.htm *Momentum word problems: http://www.cstephenmurray.com/onlinequizes/physics/momentum/momentum.htm Acceleration: change in velocity over change in time (positive acceleration – speeding up; negative acceleration – slow down) Acceleration = (velocityfinal – velocityinitial)/change in time *Calculating acceleration 1: http://www.cstephenmurray.com/onlinequizes/physics/speedexercises/acceleration.htm *Calculating acceleration 2: http://www.cstephenmurray.com/onlinequizes/physics/speedexercises/acceleration2.htm *Calculating acceleration 3: http://www.cstephenmurray.com/onlinequizes/physics/speedexercises/acceleration3.htm Physics 4A – Velocity & Acceleration (exercise) http://www.youtube.com/watch?feature=player_detailpage&v=BWHUVDGGDIc&list=PL005B8C98C0D8AB59 Work and Power Physics 5 – Work, Power & Simple Machines http://www.youtube.com/watch?v=knYvIn3jxtU&list=PL005B8C98C0D8AB59&feature=player_detailpage Energy: ability to move or change matter (do work); measured in Joules Work: force acting over a distance; measured in Joules Work = force x distance Power: work transferred per time; measured in Watts Power = work/time Physics 5A – Work & Power (exercise) http://www.youtube.com/watch?feature=player_detailpage&v=tojxIzys05U&list=PL005B8C98C0D8AB59 *Work and energy vocab: http://www.cstephenmurray.com/onlinequizes/physics/workandenergy/vocabch5no1.htm *Work pre-lesson: http://www.cstephenmurray.com/onlinequizes/physics/workandenergy/workprelesson.htm *Work problems: http://www.cstephenmurray.com/onlinequizes/physics/workandenergy/workproblems1.htm *Power problems: http://www.cstephenmurray.com/onlinequizes/physics/workandenergy/powerproblems.htm Simple Machines A device that makes work easier in 3 ways: 1. increase the distance covered (pushing a box up a ramp) 2. decrease the force required (pulling out a nail with a crowbar) 3. change the rate at which work is done *Identifying simple machines: http://www.cstephenmurray.com/onlinequizes/physics/simplemachines/simplemachinematching.htm Examples: inclined plane lever pulley wheel and axle wedge screw *Lever basics: http://www.cstephenmurray.com/onlinequizes/physics/simplemachines/leverbasics.htm *Classes of levers: http://www.cstephenmurray.com/onlinequizes/physics/simplemachines/classesoflevers.htm Efficiency: comparison between the work output (WO) and the work input (WI) of a machine. work output % Efficiency = X 100 work input Newton’s Laws Physics 3 – Newton’s Laws http://www.youtube.com/watch?list=PL005B8C98C0D8AB59&v=GCo0OMfpMZg&feature=player_detailpage *Newton’s Laws: http://www.cstephenmurray.com/onlinequizes/physics/forces/Newtonslaws.htm Force: a push or pull; needed to start or stop the motion of an object; measured in Newtons (N) Net Force: the overall force on an object; must be greater than zero for motion; no motion occurs if net force is zero (balanced) An object will move in the direction of the net (unbalanced) force. 20 N 40 N Net force = 40 N - 20 N = 20 N (right) Resistance Force: a force that opposes motion; ex. friction. Gravity: force that pulls objects in the universe toward each other > Gravity allows objects to orbit (satellites orbit the earth, earth orbits the sun) > Earth’s gravity is greater than moon’s gravity (earth is larger than moon) therefore, objects weigh more on earth than on moon (mass remains constant) > Earth’s gravitational acceleration = 9.8 m/s Weight: measures the force of gravity on an object; measured in Newtons. Weight = mass x acceleration due to gravity *Mass vs. weight: http://www.cstephenmurray.com/onlinequizes/physics/forces/MassVsWeight.htm Inertia: the property of an object that resists a change in motion. *Understanding inertia: http://www.cstephenmurray.com/onlinequizes/physics/forces/understandinginertia.htm Newton’s Laws of Motion: 1. Law of inertia: objects at rest remain at rest and objects in motion remain in motion, unless acted upon by an unbalanced force Example: seat belts protect people’s bodies from continuing to move forward when a car stops abruptly 2. Force = mass x acceleration: force causes acceleration, while mass opposes acceleration Example: if a person applies the same force, a baseball (which has less mass) will have more acceleration than a bowling ball (which has a greater mass) 3. For every force, there is an equal but opposite force Example: gas from rocket goes downward, rocket moves upward *Newton’s Second Law: http://www.cstephenmurray.com/onlinequizes/physics/forces/secondlaw1.htm Interactions of Waves Wave: disturbance that transmits energy; caused by vibration Transverse wave: vibration is perpendicular to wave direction Longitudinal wave: vibration is parallel to wave direction Amplitude: maximum distance from resting point (in absolute value) Wavelength: distance between 2 adjacent crests or troughs Frequency; f, wavelengths per time period; measured in Hertz (Hz = 1 wave/sec). wave velocity = wavelength x frequency Example: Waves Interference: two waves occupy same space; form new wave Type Alignment of Constructive crests (wave A) with crests (wave B) Destructive crests (wave A) with troughs (wave B) Result add amplitudes (= larger amplitudes) subtract amplitudes (= flat line) Medium: substance (solid, liquid, gas) in which wave travels Mechanical waves: waves that require a medium (ocean waves in water or sound waves through air or seismic waves in earth) Electromagnetic waves: waves that do not require a medium; can travel through a vacuum (empty space) at the speed of light Examples: visible light, radio waves, X-rays, microwaves Resonance: two systems vibrating at the same frequency result in an increase in amplitude Reflection: change in wave direction at boundaries of two unlike media Example: Normal: line perpendicular to surface a b Law of Reflection: Angle of incidence (a) = angle of reflection (b) Refraction: change in wave direction (bending) due to change of velocity as it passes through two unlike media Example: Normal Air (fast) Glass (slow) Light wave passing from “fast” medium into “slow” medium bends toward the normal Normal Glass (slow) Air (fast) Light wave passing from “slow” medium into “fast” medium bends away from the normal. Energy Energy: ability to move or change matter (do work); measured in Joules *Types of energy: http://www.cstephenmurray.com/onlinequizes/physics/workandenergy/typesofenergy.htm *Energy vocab: http://www.cstephenmurray.com/onlinequizes/physics/workandenergy/vocabch5no3.htm Potential Energy: energy of position (rock sitting on top of hill) Gravitational Potential Energy = mass x gravity x height Kinetic Energy: energy of motion (rock rolling down hill) Kinetic Energy = ½ (mass x velocity2) *Potential energy and kinetic energy pre-lesson: http://www.cstephenmurray.com/onlinequizes/physics/workandenergy/EpEkprelesson.htm Physics 6 – Kinetic & potential Energy http://www.youtube.com/watch?list=PL005B8C98C0D8AB59&v=SZGnHuXYbfg&feature=player_detailpage Physics 6A – Kinetic & Potential Energy (exercise) http://www.youtube.com/watch?list=PL005B8C98C0D8AB59&v=Qvwd5_N0PoE&feature=player_detailpage Physics 6B – KE & PE related http://www.youtube.com/watch?feature=player_detailpage&v=O3hPS4m8WMs&list=PL005B8C98C0D8AB59 *Kinetic vs. potential energy: http://www.cstephenmurray.com/onlinequizes/physics/workandenergy/kineticvspotentialenergy.htm *Potential energy problems: http://www.cstephenmurray.com/onlinequizes/physics/workandenergy/potentialenergyproblems.htm *Kinetic energy problems: http://www.cstephenmurray.com/onlinequizes/physics/workandenergy/kineticenergyproblems.htm Energy Form Chemical Mechanical Electrical Sound speed Light 108 m/s Solar Heat (Thermal) Description: energy stored in molecules/chemical bonds energy resulting from position or motion (Potential & Kinetic) electron movement through a conductor longitudinal waves cause vibration; increased temperature and the density of the medium increase transverse electromagnetic wave; can polarize (separate) into parallel planes; speed of light = 3 x sun-generated; provides most of Earth’s energy due to particle vibration (kinetic energy of particles); transferred in 3 ways: Natural Resource: substance that helps support life on Earth Resource Type Time to replace Examples Renewable within a person’s lifetime trees, wind Nonrenewable millions of years oil, gas, coal Inexhaustible not used up sun, wind, tides Fossil fuels: substances made over many years from the remains of living things (oil, gas, coal) Alternative fuels: energy sources other than fossil fuels Examples: solar cells, wind turbines, ethanol from corn Fuel Fossil Alternative Common Disadvantages nonrenewable, environmental pollution not always practical, expensive, disposal issues Law of Conservation of Energy Law of Conservation of Energy: energy cannot be created or destroyed but it changes from one form to another Examples: Electrical energy changes to light energy when a lamp is turned on. Chemical energy in a match changes to light energy and heat energy when lit. Heat Temperature is a measure of the average kinetic energy of the particles in a substance. Heat (measured in Joules) is the transfer of thermal energy between objects at different temperatures. Heat always flows in the same direction: from the hotter object to the cooler object. Method Radiation Conduction Convection Heat Transfer Process electromagnetic waves (heat from Sun, fire, etc) objects in contact (hot metal fork burns fingers) currents (warm air rises, cool air sinks) Circuits and Electricity Physics 7 – Circuits http://www.youtube.com/watch?list=PL005B8C98C0D8AB59&v=WeXCB55VkyQ&feature=player_detailpage Physics 7A – Electricity (exercise) http://www.youtube.com/watch?feature=player_detailpage&v=Dn08FrFFGRI&list=PL005B8C98C0D8AB59