HSC Physics Module 8.4. Moving About

Transcription

1 HSC Physics Module 8.4 Moving About

2 8.4 Moving About (30 indicative hours) Contextual outline Increased access to transport is a feature of today s society. Most people access some form of transport for travel to and from school or work and for leisure outings at weekends or on holidays. When describing journeys that they may have taken in buses or trains, they usually do so in terms of time or their starting point and their destination. When describing trips they may have taken in planes or cars, they normally use the time it takes, distance covered or the speed of the vehicle as their reference points. While distance, time and speed are fundamental to the understanding of kinematics and dynamics, very few people consider a trip in terms of energy, force or the momentum associated with the vehicle, even at low or moderate speeds. The faster a vehicle is travelling, the further it will go before it is able to stop. Major damage can be done to other vehicles and to the human body in collisions, even at low speeds. This is because during a collision some or all of the vehicle s kinetic energy is dissipated through the vehicle and the object with which it collides. Further, the materials from which vehicles are constructed do not deform or bend as easily as the human body. Technological advances and systematic study of vehicle crashes have increased understanding of the interactions involved, the potential resultant damage and possible ways of reducing the effects of collisions. There are many safety devices now installed in or on vehicles, including seat belts and air bags. Modern road design takes into account ways in which vehicles can be forced to reduce their speed. This module increases students understanding of the nature and practice of physics and the implications of physics for society and the environment. Assumed Knowledge Domain: knowledge and understanding: Refer to the Science Stages 4 5 Syllabus for the following: 5.6.2a describe qualitatively the relationship between force, mass and acceleration 5.6.2b explain qualitatively the relationship between distance, speed and time 5.6.2c relate qualitatively acceleration to change in speed and/or direction as a result of a net force 5.6.2d analyse qualitatively common situations involving motion in terms of Newton s Laws. 2

3 Concept Map Speedometer Scalars Speed Velocity Acceleration Distance Time Air Resistance Friction Vectors Inertia Force Mass Seat Belts Kinetic Energy Momentum Weight Speed Humps CrumpleZones Collisions Impulse Bull Bars 3

4 Moving About Module Plan Module Length: 7 weeks Focus Area Time Concept Resources Practical 1. Vehicles do not typically travel at a constant speed 1. identify that a typical journey involves speed changes Contexts I: pp An analysis of the external forces on vehicles helps to understand the effects of acceleration and deceleration 2. recall average speed in terms of the qualitative relationship between distance and time 3. distinguish between the instantaneous and average speed of vehicles and other bodies 4. distinguish between scalar and vector quantities in equations 5. compare instantaneous and average speed with instantaneous and average velocity 6. define average velocity as v av r t 1. Describe the motion of one body relative to another. 2. explain the need for a net external force to act in order to change the velocity of an object 3. describe the actions that must be taken for a vehicle to change direction, speed up and slow down 4. describe the typical effects of external forces on bodies including: friction between surfaces air resistance Contexts I: pp (Exp 1) plan, choose equipment or resources for, and perform a first-hand investigation to measure the average speed of an object or a vehicle 2. (Act 2) solve problems and analyse information using the formula v av r t where r = displacement 3. (Act 3) present information graphically of: displacement vs time velocity vs time for objects with uniform and nonuniform linear velocity 1. (Exp 4) plan, choose equipment or resources for and perform a first hand investigation to demonstrate vector addition and subtraction 2. (Exp 4)solve problems using vector diagrams to determine resultant velocity, acceleration and force. 3. (Act 5) analyse and effects of external forces operating on a vehicle 4. (Exp 6) gather first-hand information about different situations where acceleration is positive or negative and use vector diagrams to represent acceleration 5. outline the forces involved in causing a change in the velocity of coasting with no pressure on the accelerator pressing on the accelerator pressing on the brakes passing over an icy patch on the road climbing and descending hills following a curve in the road 6. define average acceleration as V a av t v u a av t therefore 7. define the terms mass and weight with reference to the effects of gravity 8. interpret Newton s Second Law of Motion and relate it to the equation F ma 9. identify the net force in a wide variety of situations involving modes of transport to explain the consequences of the application of that net force in terms of Newton s Second Law of Motion Contexts I: pp , Contexts I: pp (Exp 7) plan, choose equipment or resources for, and perform first-hand investigations to gather data and use available evidence to show the relationship between force, mass and acceleration using suitable apparatus 6. (Act 8) solve problems and analyse F ma information using for a range of situations 7. (Act 8) solve problems and analyse information involving F = mv 2 /r for vehicles traveling around curves. 4

5 Focus Area Time Concept Resources Practical 3. Moving vehicles have 1. identify that a moving object possesses kinetic energy and that work Contexts I: pp , kinetic energy done on that object can increase that and energy energy. 2. describe the energy transformations transformations that occur in collisions. are an important 3. define the law of conservation of aspect in energy understanding motion 4. Change of momentum relates to the forces acting on the vehicle or the driver 5. Safety devices are utilised to reduce the effects of changing momentum 1. define momentum as p mv 2. define impulse as the product of force and time 3. explain why momentum is conserved in collisions in terms of Newton s Third Law of Motion 1. define the inertia of a vehicle as its tendency to remain in uniform motion or at rest 2. discuss reasons why Newton s First Law of Motion is not apparent in many real world situations 3. evaluate the effectiveness of some safety feature of motor vehicles. Contexts I: pp Contexts I: pp , (Act 9) solve problems and analyse information to determine the kinetic energy of a vehicle and the work done using the formula: E k 1 2 mv 2 and w=fs 2. (Act 10) analyse information to trace the energy transfers and transformation in collisions leading to irreversible distortions 1. (Act 11) solve problems and analyse secondary data using p mv and Impulse F t 2. (Exp 12) perform first-hand investigations to gather data and analyse the change in momentum during collisions 3. (Act 13) solve problems that apply the principle of conservation of momentum to qualitatively and quantitatively describe the collision of a moving vehicle with: a stationary vehicle an immoveable object. another vehicle moving in the opposite direction another vehicle moving in the same direction 1. (Exp 14) identify data sources, plan, choose equipment or resources for, and gather and process first-hand data and/or secondary information and analyse information about the potential danger presented by loose objects in a vehicle 4. assess the reasons for the introduction of low speed zones and in built up areas and the addition of air bags and crumple zones to vehicles with respect to the concepts of impulse and momentum. 2. (Act 15) identify data sources, gather, process, analyse, present secondary information and use the available evidence to assess benefits of technologies for avoiding or reducing the effect of a collision 5

6 HSC Physics P3: Moving About Experiment 1: Average Speed Aim: To plan, choose equipment or resources for, and perform a first-hand investigation to measure the average speed of an object or a vehicle. o demonstrate the use of the terms dependent and independent to describe variables involved in the investigation (11.2a) o identify variables that needed to be kept constant, develop strategies to ensure that these variables are kept constant, and demonstrate the use of a control (11.2b) o design investigations that allow valid and reliable data and information to be collected (11.2c) o describe and trial procedures to undertake investigations and explain why a procedure, a sequence of procedures or the repetition of procedures is appropriate (11.2d) o predict possible issues that may arise during the course of an investigation and identify strategies to address these issues if necessary (11.2e) o identifying and/or setting up the most appropriate equipment or combination of equipment needed to undertake the investigation (11.3a) o carrying out a risk assessment of intended experimental procedures and identifying and addressing potential hazards (11.3b) o identifying technology that would be used during investigation determining its suitability and effectiveness for its potential role in the procedure or investigation (11.3c) o carrying out the planned procedure, recognising where and when modifications are needed and analysing the effect of these adjustments (12.1a) o identifying and using safe work practices during investigations (12.1d) You must devise a method using equipment listed below and/or any other equipment you bring in. Equipment Available Stop watches Inclined planes Dynamic trolleys Metre rulers You should consider the following points: Does the experiment satisfy the aim above? The safety of the experiment. Any safety notes need to be explicit. Design your own result table. Have you repeated the experiment several times to validate the results and to calculate a mean? Did you show your working? What are some possible sources of error? How could these errors be minimised or eliminated? Swap experiments with another group and collect their results at the end of the period and analyse them. Does your set of results agree with the other group who repeated your experiment? Why / why not? Do you have a conclusion? 6

7 HSC Physics P3: Moving About Activity 2: Average Speed Aim: To solve problems and analyse information using the formula v av r t where r = displacement o identify trends, patterns and relationships as well as contradictions in data and information (14.1a) o identify and explain how data supports or refutes an hypothesis, a prediction or a proposed solution to a problem (14.1c) o use models, including mathematical ones, to explain phenomena and/or make predictions (14.1f) o design and produce creative solutions to problems (14.3a) o propose ideas that demonstrate coherence and logical progression and include correct use of scientific principles and ideas (14.3b) o apply critical thinking in the consideration of predictions, hypotheses and the results of investigations (14.3c) o Formulate cause and effect relationships (14.3d) 1. Do Humphrey s Set 6 HSC Physics P3: Moving About Activity 3: Displacement/Time and Speed/Time Graphs Aim: To present information graphically of: displacement vs time speed vs time for objects with uniform and non-uniform linear velocity o using symbols and formulae to express relationships and using appropriate units for physical quantities (13.1d) o using a variety of pictorial representations to show relationships and present information clearly and succinctly (13.1e) o selecting and drawing appropriate graphs to convey information and relationships clearly and accurately (13.1f) 1. Do Humphrey s Set 7 2. Do Dyett problems

8 HSC Physics P3: Moving About Experiment 4: Vector Addition and Subtraction Aim: 1. To plan, choose equipment or resources for and perform a first hand investigation to demonstrate vector addition and subtraction 2. To solve problems using vector diagrams to determine resultant velocity, acceleration and force. o demonstrate the use of the terms dependent and independent to describe variables involved in the investigation (11.2a) o identify variables that needed to be kept constant, develop strategies to ensure that these variables are kept constant, and demonstrate the use of a control (11.2b) o design investigations that allow valid and reliable data and information to be collected (11.2c) o describe and trial procedures to undertake investigations and explain why a procedure, a sequence of procedures or the repetition of procedures is appropriate (11.2d) o predict possible issues that may arise during the course of an investigation and identify strategies to address these issues if necessary (11.2e) o identifying and/or setting up the most appropriate equipment or combination of equipment needed to undertake the investigation (11.3a) o carrying out a risk assessment of intended experimental procedures and identifying and addressing potential hazards (11.3b) o identifying technology that would be used during investigation determining its suitability and effectiveness for its potential role in the procedure or investigation (11.3c) o carrying out the planned procedure, recognising where and when modifications are needed and analysing the effect of these adjustments (12.1a) o identifying and using safe work practices during investigations (12.1d) You must devise a method using equipment listed below and/or any other equipment you bring in. Equipment Available Force meters Retort stands Metre rulers You should consider the following points: Does the experiment satisfy the aim above? The safety of the experiment. Any safety notes need to be explicit. Design your own result table. Have you repeated the experiment several times to validate the results and to calculate a mean? Did you show your working? What are some possible sources of error? How could these errors be minimised or eliminated? Swap experiments with another group and collect their results at the end of the period and analyse them. Does your set of results agree with the other group who repeated your experiment? Why / why not? Do you have a conclusion? In your discussion, you must gather information to identify how vectors are represented in equations and discuss the usefulness of using vector diagrams to assist solving problems. Each source must be referenced. 8

9 HSC Physics P3: Moving About Activity 5: Forces on Vehicles Aim: To analyse and effects of external forces operating on a vehicle o identify trends, patterns and relationships as well as contradictions in data and information (14.1a) o identify and explain how data supports or refutes an hypothesis, a prediction or a proposed solution to a problem (14.1c) o use models, including mathematical ones, to explain phenomena and/or make predictions (14.1f). Write a 400 word report with relevant equations on this issue. Record all references in a bibliography. HSC Physics P3: Moving About Experiment 6: Representing Acceleration. Aim: To gather first-hand information about different situations where acceleration is positive or negative and use vector diagrams to represent acceleration o using appropriate data collection techniques, employing appropriate technologies, including data loggers and sensors (12.2a)\ o measuring, observing and recording results in accessible and recognisable forms, carrying out repeat trials as appropriate (12.2b) 9

10 HSC Physics P3: Moving About Experiment 7: Force, Mass and Acceleration Aim: To plan, choose equipment or resources for, and perform first-hand investigations to gather data and use available evidence to show the relationship between force, mass and acceleration using suitable apparatus o demonstrate the use of the terms dependent and independent to describe variables involved in the investigation (11.2a) o identify variables that needed to be kept constant, develop strategies to ensure that these variables are kept constant, and demonstrate the use of a control (11.2b) o design investigations that allow valid and reliable data and information to be collected (11.2c) o describe and trial procedures to undertake investigations and explain why a procedure, a sequence of procedures or the repetition of procedures is appropriate (11.2d) o predict possible issues that may arise during the course of an investigation and identify strategies to address these issues if necessary (11.2e) o identifying and/or setting up the most appropriate equipment or combination of equipment needed to undertake the investigation (11.3a) o carrying out a risk assessment of intended experimental procedures and identifying and addressing potential hazards (11.3b) o carrying out the planned procedure, recognising where and when modifications are needed and analysing the effect of these adjustments (12.1a) o identifying and using safe work practices during investigations (12.1d) You must devise a method using equipment listed below and/or any other equipment you bring in. Equipment Available Stop watches Inclined planes Dynamic trolleys Ticker tape timers Metre rulers You should consider the following points: Does the experiment satisfy the aim above? The safety of the experiment. Any safety notes need to be explicit. Design your own result table. Have you repeated the experiment several times to validate the results and to calculate a mean? Did you show your working? What are some possible sources of error? How could these errors be minimised or eliminated? Swap experiments with another group and collect their results at the end of the period and analyse them. Does your set of results agree with the other group who repeated your experiment? Why / why not? Do you have a conclusion? 10

11 HSC Physics P3: Moving About Activity 8: Force Problems Aim: 1. solve problems and analyse information using F ma for a range of situations 2. solve problems and analyse information involving F = mv2/r for vehicles travelling around curves. o identify trends, patterns and relationships as well as contradictions in data and information (14.1a) o identify and explain how data supports or refutes an hypothesis, a prediction or a proposed solution to a problem (14.1c) o use models, including mathematical ones, to explain phenomena and/or make predictions (14.1f) o design and produce creative solutions to problems (14.3a) o propose ideas that demonstrate coherence and logical progression and include correct use of scientific principles and ideas (14.3b) o apply critical thinking in the consideration of predictions, hypotheses and the results of investigations (14.3c) o Formulate cause and effect relationships (14.3d) Do Humphrey s Set 15 Do Dyett problems HSC Physics P3: Moving About Activity 9: Kinetic Energy and Work. Aim: solve problems and analyse information using appropriate models to determine the kinetic energy of the vehicles using the formula: E k 1 2 mv 2 and w=fs o identify trends, patterns and relationships as well as contradictions in data and information (14.1a) o identify and explain how data supports or refutes an hypothesis, a prediction or a proposed solution to a problem (14.1c) o use models, including mathematical ones, to explain phenomena and/or make predictions (14.1f) o design and produce creative solutions to problems (14.3a) o propose ideas that demonstrate coherence and logical progression and include correct use of scientific principles and ideas (14.3b) o apply critical thinking in the consideration of predictions, hypotheses and the results of investigations (14.3c) o Formulate cause and effect relationships (14.3d) Do Humphrey s Set 24 Do Humphrey s Set 25. Do Dyett problems

12 HSC Physics P3: Moving About Activity 10: Collisions Aim: To analyse information to trace the energy transfers and transformation in collisions leading to irreversible distortions o identify trends, patterns and relationships as well as contradictions in data and information (14.1a) o identify and explain how data supports or refutes an hypothesis, a prediction or a proposed solution to a problem (14.1c) o use models, including mathematical ones, to explain phenomena and/or make predictions (14.1f Do Dyett problems HSC Physics P3: Moving About Activity 11: Momentum and Impulse Aim: solve problems and analyse secondary data using p mv and Impulse F t o identify trends, patterns and relationships as well as contradictions in data and information (14.1a) o identify and explain how data supports or refutes an hypothesis, a prediction or a proposed solution to a problem (14.1c) o use models, including mathematical ones, to explain phenomena and/or make predictions (14.1f) o design and produce creative solutions to problems (14.3a) o propose ideas that demonstrate coherence and logical progression and include correct use of scientific principles and ideas (14.3b) o apply critical thinking in the consideration of predictions, hypotheses and the results of investigations (14.3c) o Formulate cause and effect relationships (14.3d) Do Humphrey s Sets

13 HSC Physics P3: Moving About Experiment 12: Momentum in Collisions Aim: To perform first-hand investigations to gather data and analyse the change in momentum during collisions o carrying out the planned procedure, recognising where and when modifications are needed and analysing the effect of these adjustments (12.1a) o identifying and using safe work practices during investigations (12.1d) o using symbols and formulae to express relationships and using appropriate units for physical quantities (13.1d) o using a variety of pictorial representations to show relationships and present information clearly and succinctly (13.1e) o selecting and drawing appropriate graphs to convey information and relationships clearly and accurately (13.1f) o justify inferences and conclusions (14.1b) o identify and explain how data supports or refutes an hypothesis, a prediction or a proposed solution to a problem (14.1c) o predict outcomes and generate plausible explanations related to the observations (14.1d) o make and justify generalisations (14.1e) Method Part A: "Explosion" Collision 1. use a balance to determine the mass of each trolley. 2. Set up the equipment as shown below: 3. Use two carbon discs back to back in the timer. Make sure one tape goes under both and the other over both. 4. Turn on the timer and release the trolleys. 5. When the trolleys are separated by about a metre, stop the experiment. 6. Label the tapes "cart 1" and "cart 2" 7. Remove the 1 kg mass from the trolley and repeat the experiment. Results 1. Determine the average velocity for 5-dot spacings on each tape. Choose 5 dots that are fairly uniformly placed. 2. Record your results in a table format: Part B: Simple Inelastic Collision 1. Measure the masses of two trolleys. 2. Fix a piece of plasticene to the trolleys so that they will stick together when they collide. 3. Connect ticker tapes to both trolleys and start the timer. 4. Push one trolley towards the other. Label this tape "cart 1" 5. Repeat the procedure with firstly the 1 kg mass on the moving trolley and then the 1 kg mass on the stationary trolley. Results 1. Calculate the velocity before and after the collisions. 2. Calculate the momenta before and after the collisions in a table like above. Discussion (1) Is the total momentum of the system zero in each case in Part B? (2) If the total momentum was not zero in each case was the difference due to experimental error or some basic assumption error? Explain giving possible sources of error and how they could be reduced. (3) Explain why there is only a short part of the tape where there is uniform spacing between the dots. (4) Describe an experiment in which momentum changes could be studied in which both objects were moving before collision took place. Special consideration must be given to the technique for measuring velocity in such collisions. 13

14 HSC Physics P3: Moving About Activity 13: Conservation of Momentum Aim: To solve problems that apply the principle of conservation of momentum to qualitatively and quantitatively describe the collision of a moving vehicle with: a stationary vehicle a cliff face another vehicle moving in the opposite direction another vehicle moving in the same direction o identify trends, patterns and relationships as well as contradictions in data and information (14.1a) o identify and explain how data supports or refutes an hypothesis, a prediction or a proposed solution to a problem (14.1c) o use models, including mathematical ones, to explain phenomena and/or make predictions (14.1f) o design and produce creative solutions to problems (14.3a) o propose ideas that demonstrate coherence and logical progression and include correct use of scientific principles and ideas (14.3b) o apply critical thinking in the consideration of predictions, hypotheses and the results of investigations (14.3c) o Formulate cause and effect relationships (14.3d) Do Humphrey s Set 20 Do Dyett problems

15 HSC Physics P3: Moving About Experiment 14: Loose Objects in Vehicles Aim: To identify data sources, plan, choose equipment or resources for, and gather and process first-hand data and/or secondary information and analyse information about the potential danger presented by loose objects in a vehicle o demonstrate the use of the terms dependent and independent to describe variables involved in the investigation (11.2a) o identify variables that needed to be kept constant, develop strategies to ensure that these variables are kept constant, and demonstrate the use of a control (11.2b) o design investigations that allow valid and reliable data and information to be collected (11.2c) o describe and trial procedures to undertake investigations and explain why a procedure, a sequence of procedures or the repetition of procedures is appropriate (11.2d) o predict possible issues that may arise during the course of an investigation and identify strategies to address these issues if necessary (11.2e) o identifying and/or setting up the most appropriate equipment or combination of equipment needed to undertake the investigation (11.3a) o carrying out a risk assessment of intended experimental procedures and identifying and addressing potential hazards (11.3b) o identifying technology that would be used during investigation determining its suitability and effectiveness for its potential role in the procedure or investigation (11.3c) o carrying out the planned procedure, recognising where and when modifications are needed and analysing the effect of these adjustments (12.1a) o identifying and using safe work practices during investigations (12.1d) You must devise a method using equipment listed below and/or any other equipment you bring in. Equipment Available Stop watches Dynamic trolleys Ticker tape timers Metre rulers You should consider the following points: Does the experiment satisfy the aim above? The safety of the experiment. Any safety notes need to be explicit. Design your own result table. Have you repeated the experiment several times to validate the results and to calculate a mean? Did you show your working? What are some possible sources of error? How could these errors be minimised or eliminated? Swap experiments with another group and collect their results at the end of the period and analyse them. Does your set of results agree with the other group who repeated your experiment? Why / why not? Do you have a conclusion? 15

16 HSC Physics P3: Moving About Activity 15: Less Collisions Aim: To identify data sources, gather, process, analyse, present secondary information and use the available evidence to assess benefits of technologies for avoiding or reducing the effect of a collision o accessing information from a range of resources, including popular scientific journals, digital technologies and the Internet (12.3a) o extracting information from numerical data in graphs and tables as well as written and spoken material in all its forms (12.3c) o summarising and collating information from a range of resources (12.3d) o identifying practising male and female Australian scientists, and the areas in which they are currently working and in formation about their research (12.3e) o identify and apply appropriate mathematical formulae and concepts (12.4b) o evaluate the validity of first-hand and secondary information and data in relation to the area of investigation (12.4d) o assess the reliability of first-hand and secondary information and data by considering information from various sources (12.4e) o assess the accuracy of scientific information presented in mass media by comparison with similar information presented in scientific journals (12.4f) o selecting and using appropriate methods to acknowledge sources of information (13.1c) Write a 400 word report on this issue. Record all references in a bibliography. 16