S 8 P 2 Obtain evaluate and communicate
S 8 P 2. Obtain, evaluate, and communicate information about the law of conservation of energy to develop arguments that energy can transform from one form to another within a system. a. Analyze and interpret data to create graphical displays that illustrate the relationships of kinetic energy to mass and speed, and potential energy to mass and height of an object. b. Plan and carry out an investigation to explain the transformation between kinetic and potential energy within a system (e. g. , roller coasters, pendulums, rubber bands, etc. ). c. Construct an argument to support a claim about the type of energy transformations within a system [e. g. , lighting a match (light to heat), turning on a light (electrical to light)]. d. Plan and carry out investigations on the effects of heat transfer on molecular motion as it relates to the collision of atoms (conduction), through space (radiation), or in currents in a liquid or a gas (convection).
The law of conservation of energy states that: • Energy is never destroyed • Energy is never created • Energy may be transformed or converted from one form to another • Energy is constantly changing forms
Kinetic Energy • Energy of Motion • Depends on • Speed • Mass • More speed = more KE • More mass = more KE
Potential Energy • Energy of position (stored energy) • Gravitational PE depends on • Weight • Height • More weight = more PE • More height = more PE
Forms of Energy: Heat (thermal)—the vibration and movement of the atoms and molecules within substances ex. Atoms move faster in hot water vs. ice water Light (radiant)—is electromagnetic energy ex. Sunlight, X-rays, microwaves, p. 636 Electricity—energy of moving electrons, typically moving through a wire ex. lightening
Sound—energy caused by an object’s vibrations Mechanical Motion—is energy stored in a moving object or an object that can move PE + KE = mechanical energy ex. Wind, Jack in the Box
Chemical—energy stored in the bonds of atoms and molecules (is released during chemical changes when atoms are rearranged) ex. Cells in our body store chemical energy Nuclear—energy stored in the nucleus of an atom — the energy that holds the nucleus together ex. Nuclear power plants http: //www. eia. doe. gov/kids/energy. cfm? page=about_forms_of_energy-basics http: //www. bbc. co. uk/schools/ks 2 bitesize/science/physical_processes/
Conduction is the transfer of energy through matter from particle to particle as they touch. • Transfer of heat energy from atom to atom • Most effective in solids. • Heat moves from warmer substances to cooler substances.
Convection the transfer of thermal energy by the movement of a gas or liquid (a medium). The circular motion caused by density differences that result from temperature differences are called convection currents.
Radiation • the transfer of thermal energy by electromagnetic waves such as visible light and infrared waves. (See p. 636 -637). • This energy can be transferred through particles of matter OR empty space! Examples Energy from the sun Microwaves use radiation
Review Questions Which of the following converts electrical energy into mechanical? A light switch B electric stove C light bulb D electric fan
According to the Law of Conservation of Energy, if Sally throws a watermelon with 100 joules of energy off the roof of a building, how much energy should the watermelon have as it hits the ground? A. 200 joules C. 100 joules B. 150 joules D. 0 Joules
When a rock is thrown straight up into the air, it reaches its highest point and briefly comes to a complete stop before it starts to fall back to the ground. Which is greatest at the point where the rock stops? A. potential energy B. kinetic energy C. force due to gravity D. friction
A house becomes warm after air circulates in the house. What type of heat transfer happens? a. Conduction b. Convection c. Radiation
Why do we insulate our soda cans? a. To keep heat in b. To keep heat out c. To keep cold in d. To keep cold out
Where is kinetic energy the greatest? A B C D Where is potential energy the greatest? A B C D
Tonya drops a ball off a cliff as shown in the picture. Which position shows where the ball has the most kinetic energy and the least potential energy? A) A B) B C) C
Bob sat by the pool too long and his skin began to burn. What type of heat transfer occurred to make him burn? a. Conduction b. Convection c. Radiation
At which position in the pendulum swing is kinetic energy greatest? a. A b. B c. C d. D At which position in the pendulum swing is potential energy the lowest? a. A b. B c. C d. D
What type of heat transfer is happening in the picture? A. Heat to electrical B. Chemical to mechanical C. Mechanical to light D. Heat to mechanical What type of heat transfer is happening in the air around the candle? a. Conduction b. Convection c. Radiation
A gasoline-powered vehicle goes up a hill from point X to point Y. What energy transformation must occur in the car’s engine? A Chemical energy into mechanical energy B Electrical energy into light energy C Electrical energy into sound energy D Mechanical energy into light energy
When walking along an asphalt street after sundown, a person often feels heat coming off the pavement. The heat is moving from the asphalt to the person by A. Conduction B. convection C. Expansion D. radiation Heat, light, and electricity are all forms of A. Atoms B. energy C. Cells D. motion
The batteries in a flashlight make electricity using A. chemical B. solar C. heat D. mechanical In the pictures below, the candle is heating the water in the tank. Which picture shows how the water will move as it gets hot?
My dog, Ralph, wears slippers on hot days because the pavement is hot on his feet. What type of heat transfer makes his feet hot? a. Conduction b. Convection c. Radiation
Students are investigating energy transfer in the laboratory. The students use rubber bands and rulers for their investigation. They attach a rubber band to each ruler, pull the band back, and allow the band to launch from the ruler. The diagram shows their set up. The results of their investigation are shown. Which statement best describes the results of their investigation? A The more potential energy the band has, the more kinetic energy is transferred, and the farther the band travels. B The less potential energy the band has, the more kinetic energy is transferred, and the farther the band travels. C The more kinetic energy the band has, the more potential energy is transferred, and the farther the band travels. D The less kinetic energy the band has, the more potential energy is transferred, and the farther the band travels.
S 8 P 3. Obtain, evaluate, and communicate information about cause and effect relationships between force, mass, and the motion of objects. a. Analyze and interpret data to identify patterns in the relationships between speed and distance, and velocity and acceleration. (Clarification statement: Students should be able to analyze motion graphs, but students should not be expected to calculate velocity or acceleration. ) b. Construct an explanation using Newton’s Laws of Motion to describe the effects of balanced and unbalanced forces on the motion of an object. c. Construct an argument from evidence to support the claim that the amount of force needed to accelerate an object is proportional to its mass (inertia).
Velocity— • the speed of an object in a particular direction • velocity must include speed (distance over time) and direction! • ex. an airplane travels west at 600 km/h • if speed or direction changes the velocity changes
Practice: Tom is traveling west at 50 miles per hour. Sally and her family are traveling south at 50 miles per hour. Do the cars have the same velocity? Why or why not? Tom Sally
Acceleration— • The rate at which velocity changes • An object accelerates if its speed or direction changes • an increase in velocity is called positive acceleration • a decrease in velocity is called negative acceleration or deceleration • the faster the velocity changes, the greater the acceleration
Balanced Forces • Occur when the forces on an object produce a net force of 0 Newtons (N) • Will not cause a change in the motion of a moving object • Will not cause a nonmoving object to start moving • ex. Hat on your head, bird’s nest
Unbalanced Forces • Occur when the net force on an object is not 0 Newtons (N) • The forces are unbalanced • Produce a change in motion • Are necessary to start movement or change movement • ex. kicking a ball
Decide whether the following pictures represent a balanced or unbalanced force
Gravity— • A force of attraction between objects due to their masses • Law of Universal Gravity—all objects in the universe attract each other through gravitational force + Yes, you really are attracted to your science book!
• Gravity decreases as distance increases. • The more mass, the more gravitational force
Inertia— • The tendency of objects to resist any changes in motion • The more mass the more inertia More mass more inertia Less mass less inertia
Friction— • A force that opposes motion between two surfaces that are in contact • Can cause a moving object to slow down and eventually stop • Caused by roughness of surfaces
Review Questions Which characteristic of motion could change without changing the velocity of an object? A the speed B the position C the direction D the acceleration
What two forces are responsible for keeping Earth in orbit around the sun? a. Gravity and friction b. Gravity and inertia c. Friction and inertia d. Strong force and inertia Which of the following represents the velocity of a moving object?
A spring scale is pulled downward and readings are recorded. If the spring is pulled 3. 5 cm, the spring scale should read A 12 N. B 13 N. C 14 N. D 15 N.
A ball is dropped from the top of a tall building. As the ball falls, the upward force of air resistance becomes equal to the downward pull of gravity. When these two forces become equal in magnitude, the ball will A flatten due to the forces. B fall at a constant speed. C continue to speed up. D slow to a stop.
What is the net force on the cart above? A 50 N. B 150 N. C 200 N. D 350 N.
This box will increase in speed A downward and to the left. B downward and to the right. C upward and to the left. D upward and to the right.
On Earth, an astronaut has a mass of 140 kg. When the astronaut goes into space, she A. will have a mass of 140 kg, but will have less weight. B. will have less mass and weight. C. will have a mass of 140 kg, and have a weight of 140 kg. D. will have less mass and a weight of 140 kg.
A person dives out of a nonmoving boat in the direction indicated by Arrow A. Which arrow shows the direction in which the boat would move? A. Arrow A B. Arrow B C. Arrow C D. Arrow D
Which term refers to the rate of change of motion? A. Acceleration B. speed C. Momentum D. velocity The tendency for a body at rest to remain at rest is known as A. inertia B. torque C. momentum D. mass
Which force causes a moving object to slow and then stop? A. Acceleration B. inertia C. Friction D. lift
S 8 P 4. Obtain, evaluate, and communicate information to support the claim that electromagnetic (light) waves behave differently than mechanical (sound) waves. a. Ask questions to develop explanations about the similarities and differences between electromagnetic and mechanical waves. (Clarification statement: Include transverse and longitudinal waves and wave parts such as crest, trough, compressions, and rarefactions. ) b. Construct an explanation using data to illustrate the relationship between the electromagnetic spectrum and energy. c. Design a device to illustrate practical applications of the electromagnetic spectrum (e. g. , communication, medical, military). d. Develop and use a model to compare and contrast how light and sound waves are reflected, refracted, absorbed, diffracted or transmitted through various materials. (Clarification statement: Include echo and how color is seen but do not cover interference and scattering. ) e. Analyze and interpret data to predict patterns in the relationship between density of media and wave behavior (i. e. , speed). f. Develop and use a model (e. g. , simulations, graphs, illustrations) to predict and describe the relationships between wave properties (e. g. , frequency, amplitude, and wavelength) and energy. g. Develop and use models to demonstrate the effects that lenses have on light (i. e. , formation an image) and their possible technological applications.
Electromagnetic Waves— • Waves that do not need a medium—a substance through which the wave can travel • All are transverse waves Mechanical Waves— • Waves that need a medium—a substance through which the wave can travel • Can be transverse or longitudinal Ex. light, microwaves, Ex. sound waves, TV &Radio waves, X-rays ocean waves
Reflection— • occurs when waves bounce off an object • We see objects as different colors when that color is reflected back at us Ex. —A leaf appears green because it reflects green light
Absorption– • The transfer of energy carried by light to particles of matter • The farther light travels from its source the more it is absorbed by particles (this is why light becomes dimmer)
Refraction— • The bending of a wave as it passes from one medium to another • Light travels slower through matter causing light to bend
Diffraction— • The bending of waves around barriers or through openings • Amount of diffraction depends on wavelength and size of barrier or opening • Wavelength of light is small so it cannot bend very much
Electromagnetic Spectrum Low Frequency Low Energy Long Wavelength High Frequency High Energy Short Wavelength
• We see different wavelengths of visible light as different colors • Longest wavelengths are red • Shortest wavelengths are violet V I B G ROY
Sound through media— • Sound travels quickly though air • Even faster through liquids • Fastest through solids Warmer objects will conduct sound faster Why? Particles move faster in warm object so they transfer the sound faster http: //www. teachersdomain. org/asset/phy 03_vid_zlistenstick/ http: //egfl. net/Teaching/Resources/Animations/homepage. html
Sound— • a longitudinal wave caused by vibrations and carried through a substance • has to travel through a medium
Doppler Effect— • Apparent change in the frequency of a sound caused by the motion of the listener or the source of the sound • The sound will have a higher pitch as it approaches • Will have a lower pitch as it leaves
Echo— • Reflected sound wave • Occur when sound bounces off a flat hard surface
Parts of the wave— Crest—the highest point of a transverse wave Trough—the lowest point of a transverse wave Wavelength—the distance from any point on one wave to an identical point on the next wave Amplitude—the maximum distance that the particles of a wave vibrate from their rest position
Crest Rest Position Trough Amplitude wavelength
Remember: AL Amplitude/loudness PF Pitch/Frequency 1) The amplitude of a wave is related to height. 2) The greater the amplitude the louder the sound and the more energy it has.
This wave will sound loud This wave will sound quiet
Frequency—the number of waves produced in a given amount of time The frequency of a wave determines pitch. A wave with a high frequency has a high pitch. A wave with a low frequency has a low pitch.
This wave would have a high pitch. This wave would have a low pitch.
Lenses Any transparent material that refracts light Used in cameras, glasses, contacts, microscopes, telescopes, binoculars, etc.
Concave vs. Convex Lenses Concave— • A lens that diverges, or spreads out light rays; thicker at the ends and thinner in the center • Used to correct nearsightedness
Convex— • Lens that converges, or brings together, light rays; thicker in the center than at the edges • Used to correct farsightedness
Review Questions Which color reflects all colors of light? A. black B. white C. green D. red When Marcia yelled from the top of a canyon, an echo was created. This happened because the sound waves of her voice bounced back from the canyon walls. Which property of waves occurred? A. Diffraction B. reflection C. Interference D. refraction
There is only one fish in the fishbowl below. When Joseph looks down at the fish, the image he observes is closer to the surface than the actual location of the fish. Which wave characteristic does Joseph’s observation demonstrate? A. amplitude B. diffraction C. reflection D. refraction
Why are light-colored clothes cooler to wear in the summer than dark-colored clothes? A. Light-colored clothes let more air in. B. Light-colored clothes prevent sweating. C. Light colored clothes are not as heavy as dark-colored clothes. D. Light-colored clothes reflect more light than dark-colored clothes.
A family is building an outdoor shower at their cottage by hanging a plastic container from a post, as shown above. The container will be exposed to full sunlight. What color should the container be to make the water as warm as possible? A. White B. yellow C. Black D. red
In old movies, people sometimes put their ear on a railroad track to see if a train is coming. This works because the iron rail A. is heated by friction B. carries sound better than air C. is cooler than air D. is connected directly to the train
Sound A has a shorter wavelength than Sound B. This means that Sound A will A. be louder than Sound B. B. be softer than Sound B. C. have a lower pitch than Sound B. D. have a higher pitch than Sound B.
Sound can travel fastest through A. Air B. metal C. Water D. outer space
A. B. C. D. Which wave has the highest frequency? Which wave has the highest pitch? Which wave has the softest sound? Which wave has the loudest sound?
S 8 P 5. Obtain, evaluate, and communicate information about gravity, electricity, and magnetism as major forces acting in nature. a. Construct an argument using evidence to support the claim that fields (i. e. , magnetic fields, gravitational fields, and electric fields) exist between objects exerting forces on each other even when the objects are not in contact. b. Plan and carry out investigations to demonstrate the distribution of charge in conductors and insulators. (Clarification statement: Include conduction, induction, and friction. ) c. Plan and carry out investigations to identify the factors (e. g. , distance between objects, magnetic force produced by an electromagnet with varying number of wire turns, varying number or size of dry cells, and varying size of iron core) that affect the strength of electric and magnetic forces. (Clarification statement: Including, but not limited to, generators or motors. )
Electric Current— • The rate at which charges pass a given point • Expressed in amperes (amps)
How an object becomes charged… • If it loses electrons it becomes positively charged • If it gains electrons it becomes negatively charged Charged objects create electric force • Greater the charge, the greater the force • Closer the charges, the greater the force
Objects that have the same charge repel each other. Objects that have opposite charges are attracted to each other.
Objects can be charged in 3 ways… Friction—charged by rubbing Ex. rubbing balloon on hair Conduction—charged by touch Ex. touching a Van de Graaff generator Induction—charged without touching Ex. bending water with a charged balloon
Magnets • Anything that attracts iron or things made of iron • Have two poles (strongest attraction here) • Exert force on each other (magnetic force) • Surrounded by magnetic field • Can produce electrical current (this is how a generator works)
Electricity—the flow of electrons https: //www. youtube. com/watch? v=_ygm. Hnj. NYNo Electromagnetism— • Interaction between electricity and magnetism • Electric currents produce a magnetic field (attracts iron, nickel, and cobalt) • Not a permanent magnet—if electric current stops so does the magnetic field These magnets are called electromagnets Motors use electromagnets to turn electrical energy into mechanical energy.
Review Questions At which location is Earth’s magnetic field the strongest? A. 1 B. 2 C. 3 D. 4
Which electromagnet will pick up the most paper clips? A. C. B. D.
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