Presentation on theme: "a. Explain energy transformation in terms of the Law of Conservation of Energy. S8P2. Students will be familiar with the forms and transformations of."— Presentation transcript:
a. Explain energy transformation in terms of the Law of Conservation of Energy. S8P2. Students will be familiar with the forms and transformations of energy.
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
b. Explain the relationship between potential and kinetic energy. 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
c. Compare and contrast the different forms of energy (heat, light, electricity, mechanical motion, sound) and their characteristics.
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
d. Describe how heat can be transferred through matter by the collisions of atoms (conduction) or through space (radiation). In a liquid or gas, currents will facilitate the transfer of heat (convection).
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 ). 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 switchB electric stove C light bulbD 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 joulesB. 150 joules C. 100 joulesD. 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? ABCDABCD Where is potential energy the greatest? ABCDABCD
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. Ab. B c. Cd. D At which position in the pendulum swing is potential energy the lowest? a. Ab. B c. Cd. 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. ConductionB. convection C. ExpansionD. radiation Heat, light, and electricity are all forms of A. AtomsB. energy C. CellsD. 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
a. Determine the relationship between velocity and acceleration. S8P3. Students will investigate relationship between force, mass, and the motion of objects.
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? TomSally
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
b. Demonstrate the effect of balanced and unbalanced forces on an object in terms of gravity, inertia, and friction.
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!
a. Recognize that every object exerts gravitational force on every other object and that the force exerted depends on how much mass the objects have and how far apart they are.
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
c. Demonstrate the effect of simple machines (lever, inclined plane, pulley, wedge, screw, and wheel and axle) on work.
Inclined Plane— A flat slanted surface Less input force necessary, but must be exerted over a longer distance Examples: ramps, stairs,
Wedge— Device that is thick at one end and tapers to a thin edge at the other end (two inclined planes back to back) The longer and thinner the wedge, the less input force is required (same as with the inclined plane) Examples: End of an ax, knife, zipper, Push pin
Screw— An inclined plane wrapped around a cylinder The closer the threads, the greater the mechanical advantage (longer distance, but less input force needed) Examples: Jar lid, bolts, faucets The closer the threads the greater the mechanical advantage
Wheel and Axle— Two circular objects fastened together that rotate about a common axis The object with the larger diameter is the wheel and the object with the smaller diameter is the axle Multiplies your force, but you must exert your force over a longer distance Examples: door knobs, steering wheels, screw drivers wheel axle
Levers— A rigid bar that pivots or rotates about a fixed point called a fulcrum 3 different classes (types) of levers 1) 1 st Class Levers— Fulcrum (pivot point) is located between the input and output force (the load). Change the direction of the force (they can also change size or distance of the force) Examples: Seesaw, scissors, pliers, catapult Effort Fulcrum Load Effort Fulcrum Output/load
2 nd Class Levers— The load is between the fulcrum and input force (effort) Do not change the direction of the input force You must exert less force over more distance Examples: Bottle openers, wheelbarrows fulcrum Input force (effort) load
3 rd Class Levers— The input force (effort) is between the fulcrum and the load Do not change the direction of the input force Does not multiply your input force (effort) but allows you to apply a lot of force over a shorter distance Examples : Tweezers, Rake, baseball bat, Hammer
load fulcrum Input force (effort) Remember FLE 1 st Class– fulcrum in the middle 2 nd Class– load is in the middle 3 rd Class– Effort (input force) is in the middle fulcrum effort Output/load
Example: flag pole, sail boat, elevators Pulley— Grooved wheel with a rope (or chain, or cable) wrapped around it Can change the amount and direction of your input force Fixed Pulleys— A pulley attached to a structure Does not change the amount of input force Changes the direction of the input force
Moveable Pulley— A pulley attached to the object being moved Does not change the direction of the force Does increase your force—you use less force over more distance Example: a crane
Pulley System (Block and Tackle)— Combination of fixed and moveable pulleys Changes the size and direction of the force you exert
Which characteristic of motion could change without changing the velocity of an object? A the speedB the position C the directionD the acceleration Review Questions
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.
When you bend your arm at the elbow, the bones and muscles in your arm are acting as a system. What simple machine does this system represent? A. inclined planeB. pulley C.WedgeD. lever Which simple machine is a pair of scissors? A. wheel and axle B. pulley C. inclined plane D. lever
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. AccelerationB. speed C. MomentumD. velocity The tendency for a body at rest to remain at rest is known as A. inertia B. torque C. momentum D. mass
Where should Melissa position the fulcrum in order to minimize the amount of force needed to lift the box? A.Point A B. Point B C. Point C D. Point D
Which force causes a moving object to slow and then stop? A. AccelerationB. inertia C. FrictionD. lift
S8P4. Students will explore the wave nature of sound and electromagnetic radiation. a. Identify the characteristics of electromagnetic and mechanical waves.
Mechanical Waves— Waves that need a medium—a substance through which the wave can travel Can be transverse or longitudinal Ex. sound waves, ocean waves Electromagnetic Waves — Waves that do not need a medium—a substance through which the wave can travel All are transverse waves Ex. light, microwaves, TV &Radio waves, X-rays
b. Describe how the behavior of light waves is manipulated causing reflection, refraction diffraction, and absorption.
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
c. Explain how the human eye sees objects and colors in terms of wavelengths.
We see different wavelengths of visible light as different colors Longest wavelengths are red Shortest wavelengths are violet ROYGBIV
d. Describe how the behavior of waves is affected by medium (such as air, water, solids).
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
e. Relate the properties of sound to everyday experiences.
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
f. Diagram the parts of the wave and explain how the parts are affected by changes in amplitude and pitch.
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
wavelength Trough Crest Rest Position Amplitude
Remember: AL PF Amplitude/loudnessPitch/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.
Review Questions Which color reflects all colors of light? A. blackB. white C. greenD. 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. DiffractionB. reflection C. InterferenceD. 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. WhiteB. yellow C. BlackD. 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. AirB. metal C. WaterD. outer space
Which wave has the highest frequency? Which wave has the highest pitch? Which wave has the softest sound? Which wave has the loudest sound? A.B. C. D.
S8P5. Students will recognize characteristics of gravity, electricity, and magnetism as major kinds of forces acting in nature. b. Demonstrate the advantages and disadvantages of series and parallel circuits and how they transfer energy.
Types of Circuits: Series and Parallel Series Circuits— All parts of the circuit are connected in a single loop Only one path for charges to follow All loads share the same current
Disadvantages Only one pathway for moving charges If there is a break in the circuit charges stop flowing (ex. if one light blows all the lights go out) Advantages Burglar alarms use series circuits
Parallel Circuits— Loads are connected side by side Charges have more than one path on which they can travel Loads do not have the same current (each light will shine at full brightness) houses are wired in parallel
c. Investigate and explain that electric currents and magnets can exert force on each other.
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
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
Electromagnetism— Interaction between electricity and magnetism Electric currents produce a magnetic field
At which location is Earth’s magnetic field the strongest? A.1B. 2 C. 3D. 4 Review Questions
In which circuit will the bulb light up? A.B. C.D.
Which best describes a parallel circuit? A Electricity flows along one pathway. B The flow of electricity comes from one source. C Electricity flows along more than one pathway. D The flow of electricity comes from more than one source
Three identical light bulbs are connected in parallel with a battery, as shown, and all are lit. If bulb I is unscrewed and removed, what will happen to the other two light bulbs? A. Both will stay lit. B. II will go out, but III will stay lit. C. II will stay lit, but III will go out. D. Both will go out.
The bulb in the electric circuit will NOT light because A. the switch is too far away from the bulb B. the bulb has to be larger C. the wires are not long enough D. there is no energy source
Which electromagnet will pick up the most paper clips? A. B. C. D.
Which diagram is a parallel circuit? A. B. C.D.