Pearson Science Grade 8M Motion, Forces, and Energy Answers for Workbook Questions

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1 Pearson Science Grade 8M Motion, Forces, and Energy Answers for Workbook Questions Page Number Pages 9-11 Describing and Measuring Motion Pages Slow Motion on Planet Earth Pages Acceleration Question Category Describing Motion Calculating Speed Describing Velocity Graphing Motion Earth s Plates Plate Movement What is Acceleration? Answers This is one possible way to complete the graphic organizer. Accept all logical answers. What You Know A moving object changes position. You can measure how far something moves. Some things move faster than others. What You Learned You need to compare motion to a reference point. The meter is the SI unit for distance. Speed can be calculated and graphed. 1. Motion 2. A reference point is a place or object used for comparison to determine if something is in motion. 3. reference point 4. International System of units; Meter; One thousandth , Speed = Distance/Time 8. Divide the total distance the cyclist traveled by the total time. 9. velocity 10. The direction in which it is moving. 11. slope 12. true 13. 1,400 m 14. The jogger traveled no distance during these minutes; the jogger stopped. Why is the motion of plates shown over such large time spans? (Because the plates move very slowly) How has the position of North America changed over time? (North America has moved away from Africa and Europe over time.) 1. false 2. plates 3. According to this theory, Earth s plates move very slowly in various directions. 4. Circled: a, b, and d 5. true 6. Scientists can estimate how the continents moved in the past and how they may move in the future. 7. Distance = Speed Time 8. false Sample answers: Main idea: In science acceleration refers to speeding up, slowing down, or changing direction. Detail: A softball accelerates when it is thrown, because it speeds up. Detail: A softball accelerates when it is caught, because it slows down. Detail: A softball accelerates when it is hit with a bat, because it changes direction. 1. Acceleration is the rate at which velocity changes. 2. speed, direction

2 Page 17 Calculating Acceleration Graphing Acceleration Key Terms 3. acceleration 4. true 5. acceleration 6. true 7. a, b, and d 8. The moon is acceleration because it is constantly changing direction as it revolves around Earth. 9. (in left column) Speeding up; (in right column) Decreasing speed, Changing direction. 10. The change in velocity during each unit of time. 11. Acceleration = (Final speed Initial speed) / Time 12. false 13. a, b, and d 14. The speed increases over time. 15. The acceleration is constant. A 6 B 1 C 8 D 7 E 5 F 3 Page 18 The Nature of Force Pages Friction and Gravity What is a Force? Combining Forces Friction G 2 H 9 All blocks equal 15. Q. What is a force? A. A force is a push or a pull. Q. What are combined forces acting on an object called? A. The combination of all forces acting on an object is called the net force. 1. a push or a pull 2. exerting 3. a, c 4. newton 5. net force 6. added 7. positive, negative 8. start moving, stop moving, or change direction 9. true 10. balanced forces 11. false 12. zero Friction Effect on Motion: Opposes Motion Depends on: Types of surfaces; how hard they push together Measured in: Newtons Gravity Effect on Motion: Pulls objects together Depends on: Mass and Distance Measured in: Newtons 1. true 2. Friction is the force that two surfaces exert on each other when the two rub against each other. 3. opposite 4. The types of surfaces involved and how hard the surfaces push together. I 4

3 Pages Newton s First and Second Laws Pages Newton s Third Law Gravity Gravity and Motion The First Law of Motion The Second Law of Motion Newton s Third Law of Motion 5. There is very little friction between a sled or skis and the snow because the snow is smooth. Also, the snow may be partially melted, and fluid friction is relatively easy to overcome. 6. Even surfaces that seem smooth have irregular bumps that you could see with a microscope, so friction occurs even with smooth-looking objects. 7. fluid friction, sliding friction, rolling friction, static friction 8. sliding friction 9. rolling friction 10. The oil keeps the machine parts from making direct contact, and there is fluid friction between the parts instead of sliding friction. 11. gravity 12. true 13. The force of gravity acts between all objects in the universe. 14. Mass and the distance between the objects 15. Weight is the force of gravity on a person or object at the surface of a planet. 16. Weight is a measure of the force of gravity on an object, while mass is a measure of the amount of matter in an object. 17. newtons 18. false 19. An object is in free fall when the only force acting on the falling object is gravity m/s air resistance 22. terminal velocity 23. true 24. projectile 25. false 26. students should show an arrow pointing downward, labeled gravity, and a shorter arrow, labeled air resistance, pointing upward I. The First Law of Motion A. Inertia B. Inertia Depends on Mass II. The Second Law of Motion A. Changes in Force and Motion 1. force 2. Newton s first law states that an object at rest will remain at rest, and an object moving at a constant velocity will continue moving at a constant velocity unless it is acted upon by an unbalanced force 3. Inertia is an object s resistance to a change in its motion. 4. the law of inertia 5. mass 6. Acceleration depends on the object s mass and on the net force acting on the object. 7. Acceleration = Net force/mass 8. b, c 9. Force = Mass Acceleration 10. increase the force acting on it, decrease the mass of the object Q. What happens when two moving objects collide? A. Momentum is conserved. Q. What happens when a moving object collides with an unmoving object? A. All of the momentum is transferred to the unmoving object; momentum is conserved. 1. If one object exerts a force on another object, then the second object exerts a force of equal strength in the opposite direction on the first object.

4 Pages Rockets and Satellites Momentum Conservation of Momentum How Do Rockets Lift Off? What is a Satellite? Page 30 Key Terms 1. force 2. net 3. inertia 4. mass 5. newton 6. friction 7. sliding 8. fluid 9. gravity 10. free 11. air 12. weight 13. momentum 14. satellite Pages Pressure 2. action force 3. reaction force 4. equal, opposite 5. Forces can be added together only if they are acting on the same object. When one person hits a ball, the action force is exerted on the ball, while the equal reaction force is exerted back on the person. Therefore, the equal forces in this situation cannot be added together and do not cancel each other. 6. momentum 7. Momentum = Mass Velocity 8. kilograms meters per second, kg m/s 9. The total momentum of the objects that interact does not change. 10. The result of the collision is that the first train car stops and the second train car moves forward at 10 m/s. In that case, the momentum of the first train car is transferred to the second train car so momentum is conserved. Sample Main Idea: A satellite stays in orbit due to Sample Details: centripetal force inertia gravity 1. Newton s third law of motion 2. A downward action force is caused as the rocket expels exhaust gases. 3. The gases forces out of the rocket exert a reaction force equal in magnitude but opposite in direction on the rocket. 4. Students should draw two equal-sized arrows; an arrow labeled action force pointing downward, and an arrow labeled reaction force pointing upward. 5. greater 6. satellite 7. direction 8. a centripetal force 9. gravitational force 10. true 11. The satellite does not fall into Earth because Earth is curved. As a result, the satellite falls around Earth rather than into it. 12. around 13. A satellite continues to move due to its inertia. 14. gravity Q. Why does pressure decrease as elevation increases? A. Because less air is pressing down at higher elevations. Q. Why does pressure increase as depth below water increases?

5 Pages Floating and Sinking Pages Pascal s Principle What is Pressure? Fluid Pressure Variations in Fluid Pressure Buoyancy Density A. Because the amount of water exerting pressure increases. 1. Snowshoes distribute a person s weight over the large area of the snowshoes, resulting in less downward pressure on the snow compared to regular shoes. With less downward pressure, the person doesn t sink into the snow. 2. false 3. The force exerted on a surface divided by the total area over which the force is exerted. 4. d 5. a, c 6. false 7. fluid 8. Circled: a, b, d 9. In fluids, molecules are constantly moving in all directions. They are constantly colliding with each other and with any surface they meet. 10. All the forces exerted by the individual molecules in a fluid add together to make up the pressure exerted by the fluid. 11. area 12. atmospheric pressure 13. The weight of air, or the force of gravity on air s mass, produces air pressure. 14. true 15. false 16. At the higher elevation, there is less air above and therefore less weight of air to support than at a lower elevation. 17. true 18. barometer Sample Causes: The object s density is greater than the density of the fluid in which it is placed. The object takes on weight and becomes denser than the fluid. The object is compressed and becomes denser than the fluid. Sample Effect: Object sinks 1. buoyant 2. Circled: a, b, d 3. It displaces a volume of fluid equal to the object s own volume. 4. The buoyant force on an object is equal to the weight of the fluid displaced by the object. 5.false 6. The object will remain suspended at some level within the fluid. 7. density 8. Density = Mass Volume g/cm b, a, c 11. false 12. more 13. Helium is less dense than air, and objects float in air if their densities are less than air s density. A balloon filled with air does not rise because the density of the air inside the balloon is not less than air s density. 14. By pumping water out, the submarine s overall mass decreases. Since its volume remains the same, its density decreases when its mass decreases. 15. The air reduces the ship s overall density, and so allows it to float. 16. volume Q. How is pressure transmitted in a fluid? A. Pressure is transmitted equally throughout a confined fluid. Q. What are hydraulic systems? A. A hydraulic system is a system that transmits pressure in a confined fluid in order

6 Pages Bernoulli s Principle Transmitting Pressure in a Fluid Hydraulic Systems Pressure and Moving Fluids Applying Bernoulli s Principle to do work. 1. The pressure in the water increases everywhere in the bottle. 2. When force is applied to a confined fluid, a change in pressure is transmitted equally to all parts of the fluid. 3. Both pistons will experience the same force. 4. The larger piston will experience a force twenty times larger. 5. The increase in pressure on a small surface area is transmitted to another part of a confined fluid, which pushes on a larger surface area. 6. true Main Idea: Bernoulli s principle helps explain the function of many things, such as Sample detail: airplane wings Sample detail: chimneys Sample detail: flying disks Sample detail: atomizers 1. false 2. The faster a fluid moves the less pressure the fluid exerts. 3. true 4. The moving air above the tissue paper exerts less pressure than the air below the paper. The greater pressure below the paper pushes it upward. 5. true 6. upward 7. downward 8. direction of motion is to the right 9. pressure 10. Lift is an upward force on a wing created by a difference in pressure. 11. Both are curved on top. 12. Wind blowing across the top of a chimney lowers the air pressure there. The higher pressure at the bottom then pushes air and smoke up the chimney. 13. Squeezing the bulb causes air to move quickly past the top of the tube. The moving air lowers the air pressure at the top of the tube. 14. false Page 42 Key Terms 1. Pascal 2. buoyant force 3. hydraulic system 4. pascal 5. density 6. fluid 7. Archimedes 8. Bernoulli Key Term: Pressure Definition: Pressure is equal to the force exerted on a surface divided by the total area over which the force is exerted. Pages What is Work? The Meaning of Work Q. What is work? A. Work is done when a force causes an object to move in the direction of the force. Q. How is work calculated? A. Work is force times distance. Q. What is power? A. Power is the rate at which work is done. 1. You do work when you exert a force on an object that causes the object to move a distance in the same direction as the exerted force. 2. pull out books: work lift newspapers: work push on stuck car: no work hold wood in place: no work

7 Pages How Machines Do Work Pages Calculating Work Power What is a Machine? Mechanical Advantage Efficiency of Machines Inclined Plane Wedge pull sled: work hold bag: no work 3. distance 4. In carrying an object, you exert an upward force. But to do work, you must exert a force in the same direction as the object s motion. Since the object s motion is horizontal and the force extended is vertical, no work is done. 5. When you pull a suitcase with wheels, you pull at an angle to the ground. Your force has a horizontal part and a vertical part. Only the horizontal part does work because that force is in the same direction as the motion of the suitcase. 6. force, distance 7. true 8. Work = Force Distance 9. joule, or N m joule 11. Power is the rate at which work is done or the amount of work done in a unit of time. 12. true 13. Power = Work Time 14. Power = (Force Distance) Time Sample main idea: The mechanical advantage of a machine helps by: Sample details: changing force changing distance changing direction 1. A machine is a device with which you can do work in a way that is easier or more effective. 2. false 3. a, c, d 4. input force 5. output force 6. true 7. distance 8. true 9. Input force is on the handle. Output force is on the shovel. 10. The number of times a force exerted on a machine is multiplied by the machine. 11. Mechanical advantage = Output force Input force 12. output, input 13. friction 14. efficiency 15. Efficiency = (Output work Input work) 100% 16. actual 17. ideal Q. What are the three classes of levers? A. First, second, and third Q. Which type of lever always changes the direction of the input force? A. First-class levers 1. inclined plane, lever, wedge, wheel and axle, screw, pulley 2. An inclined plane is a flat, slanted surface. 3. Ideal mechanical advantage = length of incline height of incline 4. a, b, d 5. input force 6. A wedge is a device that is thick at one end and tapers to a thin edge at the other end. 7. true

8 Screws Levers Wheel and Axle Pulley Simple Machines in the Body Compound Machines Page 54 Key Terms 1. wedge 2. compound 3. output 4. fulcrum 5. work 6. axle 7. efficiency 8. lever 9. input 10. inclined 11. pulley 12. machine 13. joule 14. screw Pages What is Energy? 8. true 9. A screw is an inclined plane wrapped around a cylinder. 10. threads 11. The input force is applied to the top of the screw. As the screw turns, the threads exert an output force on the wood. 12. A lever is a rigid bar that is free to pivot, or rotate, around a fixed point. 13. fulcrum 14. a, b, c 15. first class levers: fulcrum is 1/3 of the way across from the left second class levers: fulcrum is close to the left side third class levers: fulcrum is close to the left side 16. Second-class lever First-class lever Third-class lever 17. Ideal mechanical advantage = distance from fulcrum to input force distance from fulcrum to output force 18. A wheel and axle is a simple machine made of two circular objects that are fastened together and that rotate around a common axis. 19. Ideal mechanical advantage = Radius of wheel Radius of axle 20. A pulley is a grooved wheel with a rope (or chain, or even a steel cable) wrapped around it. 21. fixed pulley 22. moveable pulley 23. They consist of bones and muscles. 24. tendons 25. The joint near where the tendon is attached to the bone acts as the fulcrum. 26. Black arrow: output force White arrow: input force Fulcrum: close to the elbow 27. wedges 28. When you bite down on something, the wedge shape of your teeth produces enough force to break it in half, just as an ax is used to split a log. 29. A compound machine is a machine that utilizes two or more simple machines. 30. You must know the mechanical advantage of each simple machine utilized in the compound machine. Answers will vary. Accept all logical answers. Sample Answers: What I know: The joule is the unit of work. Energy and work are related. What I learned: The joule is the unit of energy.

9 Pages Forms of Energy Pages Energy Transformations and Conservation Energy, Work, and Power Kinetic Energy Potential Energy Mechanical Energy Other Forms of Energy Energy Transformations Transformations Between Potential Work can be thought of as the transfer of energy. 1. energy 2. When an object or organism does work on an object, some of the energy is transferred to the object. 3. Power is the rate at which energy is transferred. 4. a. kinetic energy b. potential energy 5. The energy of motion 6. mass, velocity 7. increases 8. Kinetic energy = 1/2 Mass Velocity 2 9. quadruple 10. Potential energy is energy that is stored and held in readiness. 11. elastic potential energy 12. gravitational potential energy 13. Gravitational potential energy = Weight Height 14. true Answers will vary. Accept all logical answers. Mechanical energy: The combination of an object s potential and kinetic energy. Thermal energy: The total potential and kinetic energy of the particles in an object. Electrical energy: Energy carried in moving electric charges. Chemical energy: Energy stored in the chemical bonds in compounds. Electromagnetic energy: Energy that travels in waves that have some electrical properties and some magnetic properties. Nuclear energy: Energy stored in the nucleus of atoms. 1. potential and kinetic 2. I would calculate mechanical energy by adding together the potential and kinetic energy of an object. 3. joules 4. true 5. electrical energy 6. chemical energy 7. nuclear energy 8. Mechanical energy: School bus moving, frog leaping, sounds being made Thermal energy: Ice cream melting, object feeling warm Chemical energy: Foods, matches, stores in body cells Electrical energy: Static shock, batteries, power lines Nuclear energy: Nuclear fission, nuclear fission Electromagnetic energy: Visible light, ultraviolet radiation, microwaves, infrared radiation Q. What is an energy transformation? A. An energy transformation occurs when one kind of energy changes form to become another kind of energy. Q. What energy transformations occur between potential and kinetic energy? A. As an object changes position or motion, energy is converted between potential and kinetic and energy. Q. What is the law of conservation of energy? A. The law of conservation of energy states that energy cannot be created or destroyed as it changes form. 1. energy transformation 2. true 3. The body converts the chemical energy in food to the mechanical energy needed to move muscles. 4. potential energy 5. Its kinetic energy increases and it potential energy decreases.

10 Pages Energy and Fossil Fuels and Kinetic Energy Conservation of Energy Formation of Fossil Fuels Use of Fossil Fuels Page 64 Key Terms 1. energy 2. kinetic energy 3. potential energy 4. mechanical energy 5. thermal energy 6. chemical energy 7. electrical energy 8. electromagnetic energy 9. nuclear energy 10. energy transformation 11. law of conservation of energy 12. fossil fuels 13. power Pages Temperature, Thermal Energy, and Heat 6. Maximum potential energy is to the left and right of the swinging object. Maximum kinetic energy is when the object points straight down. 7. When one form of energy is converted to another, no energy is destroyed in the process. 8. thermal 9. b 10. The theory of relativity explains that energy can sometimes be created by destroying matter. 11. true This is one possible way to complete the graphic organizer. Accept all logical answers. Q. What energy transformation occurs in the sun? A. The sun transforms nuclear energy to electromagnetic energy. Q. What energy transformation occurs in plants? A. Plants transform electromagnetic energy into chemical energy. 1. true 2. a, c, d 3. the sun 4. During nuclear fusion, nuclear energy is transformed to electromagnetic energy. 5. Electromagnetic energy from the sun is transformed to chemical potential energy. 6. It is released by burning the fossil fuels. 7. combustion 8. The fuel s chemical potential energy is transformed to thermal energy. 9. generators Energy Measured Units Temperature Thermal Energy Heat Average kinetic energy of particles Total energy of all particles in an object Transferred energy F, C, or kelvins joules joules Temperature 1. true 2. Temperature is a measure of the average kinetic energy of the individual particles

11 Pages The Transfer of Heat Thermal Energy and Heat Specific Heat How is Heat Transferred? Heat Moves One Way of an object. 3. The particles in a mug of hot cocoa are moving faster. 4. a. Fahrenheit scale b. Celsius scale c. Kelvin scale 5. Fahrenheit 6. Celsius 7. Kelvin 8. degrees Fahrenheit 9. Celsius scale 10. absolute zero 11. Temperature Scale Scale Absolute Zero Water freezes Water boils Fahrenheit -460º 32º 212º Celsius -273º 0º 100º Kelvin thermal 13. a, c, d 14. It is the amount of energy required to raise the temperature of 1 kilogram of the substance by 1 kelvin. 15. joules per kilogram-kelvin, or J/(kg K) 16. temperature 17. a, c, d 18. Change in energy = Mass Specific heat Change in temperature Sample main idea and details: Main idea: Heat can be transferred in three ways. Detail: Heat can be transferred by radiation. Detail: Heat can be transferred by convection Detail: Heat can be transferred by conduction. 1. a, c, d 2. The fast-moving particles of the hot water collide with the particles of the spoon, causing the particles of the spoon to move faster. As the particles move faster, the metal spoon becomes hotter. 3. Heat is transferred by the movement of currents within a fluid. 4. convection current 5. Convection currents should be drawn starting in the center of the pot moving to the outside of the pot. 6. false 7. See below. Heat Transfer Process How Heat Moves Example Conduction Transferred from on particle of Metal spoon in hot water matter to another without the movement of matter itself Convection Transferred by the movement of Pot of hot water on a currents within a fluid stove, heating a building or the atmosphere Radiation Transferred by electromagnetic Bonfire, heat lamp, the waves sun heating Earth 8. The temperature of the substance giving off the heat decreases, while the temperature of the substance receiving the heat increases. 9. There is no such thing as coldness.

12 Pages Thermal Energy and States of Matter Pages Uses of Heat Conductors and Insulators States of Matter Changes of State Thermal Expansion Heat Engines 10. conductor 11. insulator 12. a. insulator b. insulator c. insulator d. conductor e. conductor f. insulator Sample answers: state Water is found in the liquid state at room temperature. change of state When the ice cubes in lemonade melt, it is a change of state. melting When snow is melting, a solid becomes a liquid. freezing When water is freezing, a liquid is becoming a solid. evaporation The puddle grew smaller as evaporation occurred and the water became a gas. boiling I could tell that the water was boiling because gas bubbles rose to the surface. condensation Water collected on the outside of the drinking glass due to condensation. thermal expansion Thermal expansion caused the road to buckle during the heat wave. 1. true 2. b, c, d 3. solid 4. a, c 5. solid 6. gas 7. It is the physical change from one state of matter to another 8. thermal energy 9. diagonal line to the left of freezing/melting label: solid diagonal line to the right of freezing/melting: liquid diagonal line to the right of condensation/ vaporization: gas 10. melting 11. melting point 12. freezing 13. freezing point 14. Vaporization is the process by which matter changes from the liquid state to the gas state. 15. evaporation 16. boiling 17. boiling point 18. condensation 19. thermal expansion 20. expand Sample steps in the cycle diagram: refrigerant absorbs heat; refrigerant flows to compressor and pressure increases; gas refrigerant releases heat to the room and changes to a liquid; liquid refrigerant flows through the expansion valve, pressure drops, and temperature of refrigerant drops 1. mechanical 2. heat engine 3. combustion 4. They are classified according to whether combustion takes place outside the engine or inside the engine. 5. In an external combustion engine fuel is burned outside the engine; an example is a steam engine. In an internal combustion engine, fuel is burned inside the engine; examples include diesel and gasoline engines. 6. a piston 7. stroke 8. thermal

13 9. intake; compression; power; exhaust. Cooling Systems 10. warmer 11. An electric motor provides the energy. 12. It loses energy in the compression motor. Page 78 Key Terms 1. thermal expansion 2. heat 3. melting 4. evaporation 5. convection 6. refrigerant 7. insulator 8. heat engine 9. absolute zero 10. conductor 11. change of state Circled term: temperature