HSC PHYSICS INVESTIGATIONS. Brian Shadwick

Transcription

1 HSC PHYSICS INVESTIGATIONS Brian Shadwick

2 2008 First published 2008 Private Bag 7023 Marrickville NSW 1475 Australia Tel: (02) Fax: (02) All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, electronic, mechanical, photocopying, recording or otherwise, without the prior permission of. ABN

3 Contents Introduction Verbs to Watch v vi Dot Points Space Motors and Generators From Ideas to Implementation From Quanta to Quarks Astrophysics vii ix xi xiii xv Investigations Space 1 Motors and Generators 33 From Ideas to Implementation 79 From Quanta to Quarks 119 Astrophysics 135 Appendix Answers 167 Data Sheet 173 Formula Sheet 174 Periodic Table 175 iii Contents

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5 Introduction This book provides all the instructions and other information needed for you to carry out the mandatory experiments listed in column 3 of the NSW HSC Board of Studies Physics syllabus. In some cases, more than one experiment has been suggested. The syllabus requires 35 hours of practical work, but this need not all be experimental work. Practical work includes research to gather, process and analyse information, presenting information in written or spoken format, and solving problems. It is only the experimental and research aspects of the course that have been included in this book. These have been selected on the criteria that they are the topics traditionally given to students as research topics. Solving problems is covered in two other books in the series, Dot Point HSC Physics Multiple Choice and Dot Point HSC Physics. Investigations suggesting or requiring the use of computer simulations or data loggers have not been included because schools will have access to different resources for these. Schools are in a better position to design their own activities specific to their resources. The dot point numbers allocated to each experiment reflect the numbers allocated to that dot point in the other books in the series. Remember that these numbers are author derived and do not appear in the syllabus. In completing the activities in this book, you will have satisfied those aspects of the practical work required by the syllabus as detailed in column 3 of the syllabus document. Note that the purpose of practical work is to increase your skills in the activities required to complete the exercise. For this reason only answers to exercises that do not void the work that you need to do in order to develop these skills have been supplied. v Introduction

6 Verbs to Watch account/account for State reasons for, report on, give an account of, narrate a series of events or transactions. analyse Identify components and the relationships among them, draw out and relate implications. apply Use, utilise, employ in a particular situation. appreciate Make a judgement about the value of something. assess Make a judgement of value, quality, outcomes, results or size. calculate Determine from given facts, figures or information. clarify Make clear or plain. classify Arrange into classes, groups or categories. compare Show how things are similar and different. construct Make, build, put together items or arguments. contrast Show how things are different or opposite. critically (analyse/evaluate) Add a degree or level of accuracy, depth, knowledge and understanding, logic, questioning, reflection and quality to an analysis or evaluation. deduce Draw conclusions. define State the meaning of and identify essential qualities. demonstrate Show by example. describe Provide characteristics and features. discuss Identify issues and provide points for and against. distinguish Recognise or note/indicate as being distinct or different from, note difference between things. evaluate Make a judgement based on criteria. examine Inquire into. explain Relate cause and effect, make the relationship between things evident, provide why and/or how. extract Choose relevant and/or appropriate details. extrapolate Infer from what is known. identify Recognise and name. interpret Draw meaning from. investigate Plan, inquire into and draw conclusions about. justify Support an argument or conclusion. outline Sketch in general terms; indicate the main features. predict Suggest what may happen based on available data. propose Put forward (a point of view, idea, argument, suggestion etc) for consideration or action. recall Present remembered ideas, facts or experiences. recommend Provide reasons in favour. recount Retell a series of events. summarise Express concisely the relevant details. synthesise Put together various elements to make a whole. Verbs to Watch vi

7 Space Dot Point Page 1. Gravitational field 1.3 Gather secondary information to 3 predict the acceleration due to gravity on other planets. 1.4 Perform an experiment to determine 5 the acceleration due to gravity using a pendulum. Interlude exercise: Validity, reliability 10 and accuracy of experimental results. 2. Rocket launches and gravity 2.7 Perform an investigation to calculate 15 initial and final velocity, range, maximum height and time of flight of a projectile. Predicting the range of a projectile. 15 The nature of the vertical acceleration 19 of a projectile. Dot Point Page 2.13 Identify data sources, gather, analyse 23 and present information on the contribution to space research of one of: Tsiolkovsky, Oberth, Goddard, Esnault-Pelterie, O Neill or Von Braun. 4. Understanding time and space 4.3 Gather and process information to 25 interpret the results of the Michelson-Morley experiment. 4.6 Perform an investigation to distinguish 29 between non-inertial and inertial frames of reference. vii Space

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9 Motors and Generators Dot Point Page 1. Current-carrying conductors 1.6 Perform an experiment to 35 demonstrate the motor effect. The effect of increasing the current. 35 The effect of increasing the magnetic 37 field strength Identify data sources, gather and 39 process information to describe the application of the motor effect in a galvanometer Identify data sources, gather and 41 process information to describe the application of the motor effect in a loudspeaker. 2. Generating electricity 2.2 Perform an investigation to model the 43 generation of an electric current. 2.3 Plan and perform an experiment to 47 predict and verify the effect on a generated current of the distance between the coil and the magnet, the strength of the magnet, and the relative motion between the coil and the magnet Gather, analyse and present information 51 to explain how induction is used in cooktops Gather secondary information to identify 53 how eddy currents have been utilised in electromagnetic braking. 3. Generators 3.4 Gather secondary information to discuss 55 advantages and disadvantages of AC and DC generators and relate these to their use. Dot Point Page 3.5 Plan, choose equipment for and 57 perform an experiment to demonstrate the production of an alternating current. 3.9 Analyse secondary information on the 59 competition between Westinghouse and Edison to supply electricity to cities Gather and analyse information to 63 identify how transmission lines are insulated from supporting structures and protected from lightning strikes. 4. Transformers 4.5 Gather, analyse and use available 65 evidence to discuss how difficulties of heating caused by eddy currents in transformers may be overcome. 4.6 Perform an experiment to model the 67 structure and working of a transformer and demonstrate how secondary voltage is produced. 4.7 Gather and analyse secondary 73 information to discuss the need for transformers in the transfer of electrical energy from a power station to its point of use. 5. Motors and energy changes 5.2 Perform an investigation to demonstrate 75 the principle of an AC induction motor. 5.3 Gather, process, and analyse 77 information to identify some of the energy transfers and transformations involving the conversion of electrical energy into more useful forms in the home and industry. ix Motors and Generators

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11 From Ideas to Implementation Dot Point Page 1. Cathode rays 1.3 Perform an investigation to identify 81 the properties of cathode rays using various discharge tubes. 1.4 Perform an investigation to observe the 85 different patterns of striations in cathode ray tubes at different pressures. 2. The photoelectric effect and black body radiation 2.3 Perform an experiment to show the 87 production and reception of radio waves. 2.5 Identify data sources, gather, process 89 and analyse data to identify Einstein s contribution to quantum theory and its relation to black body radiation. 2.6 Identify data sources, gather, process 89 and analyse data to assess Einstein s contribution to quantum theory and its relation to black body radiation Identify data sources, gather, process, 91 and analyse data to identify and present information to summarise the use of the photoelectric effect in photocells Process information to discuss Einstein 95 and Planck s differing views about whether scientific research is removed from social and political forces. 3. Transistors 3.5 Perform an experiment to model the 97 behaviour of semiconductors. Computer simulation. 97 Building a physical model. 101 Dot Point Page 3.10 Gather, process, and analyse data to 103 identify and present information to discuss how shortcomings in available communication technology led to the invention of the transistor Identify data sources, gather, 105 process, and analyse data to assess the impact of the invention of transistors on society with particular reference to their use in microchips and microprocessors Identify data sources, gather, process 107 and present information to summarise the effect of light on semiconductors in solar cells. 4. Superconductors 4.6 Process information to identify some of 109 the metals, metal alloys and compounds that exhibit superconductivity and their critical temperatures Perform an experiment to demonstrate 111 magnetic levitation. Simple magnetic levitation. 111 Maglev and the Meissner effect Gather and process information to 115 describe how superconductors and magnetic fields have been applied to develop maglev trains Process information to discuss possible 117 applications of superconductivity and the effects of those applications on computers, generators, motors and the transmission of electricity through power grids. xi From Ideas to Implementation

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13 From Quanta to Quarks Dot Point Page 1. Models of the atom 1.3 Perform a first-hand investigation to 121 observe the visible components of the hydrogen spectrum. 1.8 Process and present diagrammatic 123 information to illustrate Bohr s explanation of the Balmer series Analyse secondary information to 125 identify difficulties with the Rutherford-Bohr model of the atom. 2. Development of quantum physics 2.6 Gather, process, analyse and present 127 information and use available evidence to assess the contributions made by Heisenberg and Pauli to the development of atomic theory. Dot Point Page 3. Development of nuclear physics 3.6 Perform a first-hand experiment or 129 gather secondary information to observe radiation emitted from a nucleus using a Wilson cloud chamber or similar detecting device. 4. Applications of nuclear physics 4.2 Gather, process, and analyse information 131 to assess the significance of the Manhattan Project to society. 4.4 Identify data sources, gather, process 133 and analyse information to describe the use of a named isotope in medicine, agriculture and engineering. xiii From Quanta to Quarks

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15 Astrophysics Dot Point Page 1. Observing celestial objects 1.6 Identify data sources, plan, choose 137 equipment and resources for, and perform an investigation to demonstrate why it is desirable for telescopes to have a large diameter objective lens or mirror in terms of both sensitivity and resolution. 2. Using astrometry to determine distance of celestial objects 2.5 Gather and process information 141 to determine the relative limits to trigonometric parallax distance determinations using recent ground-based and space-based telescopes. 3. Using spectroscopy to gather information 3.4 Perform a first-hand investigation 143 to examine a variety of spectra produced by discharge tubes, reflected sunlight, or incandescent filaments. Dot Point Page 4. Using photometry for determining distance and comparing celestial objects 4.7 Perform an investigation to demonstrate 147 the use of filters for photometry. 4.8 Identify data sources, gather, 151 process and present information to assess the impact of improvements in measurement technologies on our understanding of celestial objects. 5. Binary and variable stars 5.5 Perform an investigation to model the 153 light curves of eclipsing binaries using computer simulation. 6. Evolution of stars 6.7 Present information by plotting 157 Hertzsprung-Russell diagrams for nearby or brightest stars; stars in a young open cluster; stars in a globular cluster. 6.9 Present information by plotting on a 161 Hertzsprung-Russell diagram the pathways of stars of 1, 5 and 10 solar masses during their life cycle. xv Astrophysics

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17 DOT POINT Space 1 Space

18 Notes Space 2

19 1.3 Predict the acceleration due to gravity on other planets. Purpose To determine the value of the acceleration due to gravity on other heavenly objects. Theory The gravitational force exerted by a planet or moon on any object gives that object its weight. This idea is summarised in Newton s second law and gravitational equations: Where m o = mass of the object (kg) m p = mass of the moon (or planet) g = value of acceleration due to gravity (m s 2 ) G = Newton s gravitational constant = (N m 2 kg 2 ) r = radius of planet (or moon) (assuming object is on the surface) weight = force of gravity acting on an object (N) From this we get the following equation for predicting the acceleration due to gravity on the surface of a planet (or moon): Note that if we use Newton s gravitational equation to find the force of gravity acting between two objects in the Universe, say, the Earth and its Moon, then r is the distance between the centres of mass of the two objects. That is, r = radius of Earth + distance between Earth and Moon + radius of Moon 3 Space

20 Instructions Using the equation given research the required data and then calculate the value of the acceleration due to gravity on the surface of each of the heavenly objects in the table. Information about the Solar System and other aspects of the Universe are readily available from NASA websites. Heavenly object Mass of heavenly object (kg) Radius of heavenly object (m) Value of acceleration due to gravity on surface of heavenly object (m s 2 ) Planets of the Solar System Mercury Venus Earth Mars Jupiter Saturn Uranus Neptune Pluto (Dwarf planet) Moons in the Solar System Earth s Moon Phobos (Mars) Deimos (Mars) Ganymede (Jupiter) Callisto (Jupiter) Io (Jupiter) Titan (Saturn) Titania (Uranus) Oberon (Uranus) Triton (Neptune) Charon (Pluto) Space 4

21 1.4 Perform an investigation to determine a value for the acceleration due to gravity using pendulum motion. Purpose To determine the value of the acceleration due to gravity using a pendulum. Equipment needed Retort stand, boss head, clamp, string, mass carrier, slotted masses, stopwatch, metre rule. Equipment set-up Boss head and clamp String Retort stand Mass carrier Theory The swing of a pendulum is due to the force of gravity acting on the bob (the mass at the end of the string). The period of the pendulum (the time it takes for one complete swing back and forth) depends on two variables only the length of the string and the acceleration due to gravity. The mathematical formula for the period of a pendulum is: Where T = period in seconds (s) l = length of pendulum (m) g = acceleration due to gravity (m s 2 ) 5 Space

22 Part A Instructions 1. Set up the apparatus to make your pendulum. Make sure the string is tied tightly enough so that it does not slip on the clamp, and that the pendulum hangs over the edge of the bench. 2. Tie a mass carrier to the bottom end of the string, and add one 50 g mass to the carrier. Measure the length of the pendulum string from its anchor point on the clamp to the middle of the pile of masses on the mass carrier (the approximate centre of mass). 3. Set the pendulum swinging (no more than 30 o deviation from normal to start the swing) and use the stopwatch to time 20 complete swings. 4. Repeat this measurement for at least 5 different lengths of the pendulum. 5. Record all your measurements in the table below and use them to complete the other columns in the table. Results Experiment run Length of the pendulum (m) Time for 20 swings (s) Average time for 20 swings (s) Average period of the pendulum T (s) Average period squared T 2 (s 2 ) 1(a) 1(b) 1(c) 2(a) 2(b) 2(c) 3(a) 3(b) 3(c) 4(a) 4(b) 4(c) 5(a) 5(b) 5(c) Space 6

23 Analysis of results 1. Note that from the equation: We get, on squaring and rearranging: So, we need to graph l versus T 2 in order to obtain a straight line graph. Do this on the axes below. Place the length of the pendulum, the independent variable, on the x-axis. 2. Using the gradient of your graph, and the equation above, calculate a value for the acceleration due to gravity Conclusion Space

24 Questions Identify three factors you have controlled in this experiment Use your graph to predict the pendulum length for a 1-second swing Explain the reason you were asked to measure the time for 20 swings rather than simply measuring the period of the pendulum The gravitational pull of the Moon is about one sixth that of Earth. Predict a value for the acceleration due to gravity on the surface of the Moon Suggest two safety measures that should be taken when doing this experiment Calculate the accuracy of your final result by comparing it with the value of the acceleration due to gravity at sea level on Earth (= 9.8 m s 2 ) and finding your percentage error Suggest how the accuracy of this experiment could be improved Space 8

25 Part B Instructions In the theory in Part A it was stated that the period of the pendulum depends on two variables only the length of the string and the acceleration due to gravity. 1. Design and carry out an experiment using the same apparatus you used in Part A, to show that the period of a pendulum is independent of the mass of the pendulum bob. 2. Write up your experiment, including all results and graphs if necessary, in the space below Space

26 Interlude exercise: Validity, reliability and accuracy of experimental results. It is important that the results of experiments have three properties: validity, reliability, and accuracy. The experiments that you do during this course will not involve life or death decisions those made by medical researchers, engineers, space scientists, car safety experts, food additive scientists, and nuclear researchers to name just a few, whose experiments could affect the safety or lives of people. Because you may eventually enter into a research field, it is important that you develop understandings about these properties of experimental results now so that you will be a better researcher in the future. Instructions Use your textbook, your library or other resources to complete the tasks below. Validity Definition: How do we ensure our experiments are as valid as possible? Reliability Definition: How do we ensure our experiments are as reliable as possible? Space 10

27 Accuracy Definition: Accuracy is often reported as a percentage error. Explain, giving an example, how this can be done How do we ensure our experiments give as accurate a result as possible? It is important when you do the practical exercises in this course (or any other) that you take the ideas in the tables above into consideration when designing and carrying out those exercises. By doing this, way, your results should be more valid, more reliable and more accurate that they otherwise might be. However, there is still one more aspect of reliability and accuracy that needs to be considered. When we analyse experimental results, it is important if possible, to graph those results and use data from the graph to determine our final answer rather than to make mathematical calculations of individual results and then taking a mathematical average of the calculated answers. Doing this helps to minimise systematic errors. These are errors which appear in every reading taken. They can be due to errors in equipment (for example a stopwatch that runs too fast) or human error (human reaction time or poor experimental technique). Systematic errors will usually affect all results in the experiment in the same way they will always be higher or lower than they should be. To illustrate this point, follow the instructions below to analyse the data provided for an experiment involving a swinging pendulum. The tables show the results of two identical experiments to find a value for the acceleration due to gravity using a pendulum similar to the experiment you have just done. The first table shows the results done using a stopwatch which was running faster than it should. The second table shows results using an accurate stopwatch. Analyse the data as instructed. 11 Space

28 Questions I.E.1 Make calculations to complete each table. Table 1: Results incorporating human and watch error of 0.5 s for each reading. Length of the pendulum (m) Time for 20 swings (s) Period of the pendulum T (s) Period squared T 2 (s 2 ) Calculated value for g using: Average calculated value for g Accepting accurate value for g as 9.8 m s 2, calculate the percentage error of this result Table 1: Results using stopwatch running accurately. Length of the pendulum (m) Time for 20 swings (s) Period of the pendulum T (s) Period squared T 2 (s 2 ) Calculated value for g using: Average calculated value for g Accepting accurate value for g as 9.8 m s 2, calculate the percentage error of this result Space 12

29 I.E.2 Graph each set of results (T 2 versus l ) on the grids below, and use the graphs to determine values for g. Graph for data with systematic error: Graph for accurate data: 13 Space

30 I.E.3 Complete the table. Gradient of graph Value of g found using: Percentage error if correct value is 9.8 m s 2 Calculations for values with systematic error Calculations for accurate values I.E.4 On the basis of your analysis, comment on the effect of analysing experimental data using graphical analysis as opposed to mathematical calculations from a formula I.E.5 In the pendulum experiment we plot T 2 against l, not T against l. Explain why we do this I.E.6 Sketch the graph you would expect to obtain if you did plot T against l. I.E.7 Explain why, in any experiment, a graph the shape of your sketch graph in I.E.6 is not an appropriate graph to draw a conclusion from Space 14

31 2.7 Perform an investigation to calculate initial and final velocity, range, maximum height and time of flight of a projectile: Predicting the range of a projectile. Purpose To predict the range of a projectile knowing its initial horizontal velocity and time of flight. Equipment needed Ramp (piece of wood with groove cut down its length or length of aluminium window track), steel ball bearing, stopwatch, metre rule, polyfoam cup. Equipment set-up Ramp Ball bearing Measured and timed distance Path taken by ball bearing Floor X Point X, directly below launch point Foam cup Theory As a ball rolls down an incline its gravitational potential energy will be converted into kinetic energy. If the ball starts from a constant distance up the ramp, then its velocity at the bottom of the ramp will be constant. If we ignore friction, then this will be the speed at which the ball rolls across the benchtop and launches itself towards the floor. This can be determined by timing how long the ball takes to roll a distance of (say) 0.5 metres across the benchtop using the equation: distance rolled across benchtop time taken to roll this distance As determined by Galileo, the vertical and horizontal components of the velocity of a projectile are independent of each other. While the vertical velocity is accelerated by gravity, the horizontal velocity is constant. The horizontal range of a projectile can therefore be predicted using: 15 Space

32 Part A Instructions: Finding the time of flight 1. Hold the ball bearing with its lower surface exactly level with the benchtop. 2. Let it go and time how long it takes to fall to the floor. This will be the time of flight of the ball. 3. Repeat this measurement five times and calculate the average time. 4. Record your results in Table A. This will be needed in Part B of the experiment. Table A Drop Average time of flight (s) Time (s) Part B Instructions: Predicting the range 1. Set up the apparatus about 50 cm from the edge of the bench, and mark starting positions of the ball on the ramp (say, 20, 30, 40, 50 cm up to 1.0 m up the ramp). 2. Make a chalk mark on the bench exactly 1.0 m from the edge of the bench. 3. Roll the ball down the ramp from each measured starting point at least five times and measure the time it takes to travel the 0.5 m across the benchtop. (DO NOT allow the ball to complete its journey to the floor you MUST catch it as it leaves the edge of the bench.) 4. Record all your measurements in Table B and use them to make the calculations necessary to complete the other rows in the table. Table B Run Distance ball released from up ramp (m) Time 1 Time for ball to travel across bench (s) Time 2 Time 3 Time 4 Time 5 Average time across bench (s) Launch speed (m s 1 ) Time of flight from Part A (s) Predicted range of ball (m) Space 16

33 5. On the axes below, draw a graph of the launch velocity of the ball against its predicted range. Testing your predictions 1. Transfer the predicted ranges of the ball from Table B into Table C below. 2. Measure these distances out from the point on the floor directly under the edge of the bench (point X). 3. Launch the ball from the appropriate distance up the ramp to see if it lands on the marks you have made on the floor. If it does, then your predictions were correct. 4. Record how far away from each mark the ball lands as your results for this part of the experiment. Table C Predicted range of ball (m) How far ball lands away from mark (m) Conclusion Space

34 The final test! 1. On the axes below graph the height of the ball bearing up the ramp against its launch velocity. 2. Your teacher will now give you a specific distance up the ramp. Use the graphs you have drawn to predict the launch velocity of the ball and its range. Put these values in Table D. Table D Distance up ramp Predicted launch velocity Predicted range of ball (m) 3. Now place the polyfoam cup in position on the floor at your predicted range. 4. Roll the ball down the ramp from the specified distance and see if it lands in the cup. If it does well done! Question Why were you asked to take several readings for the time for the ball to fall in Part A, and for the time for the ball to roll across the benchtop in Part B Space 18

35 2.7 Perform an investigation to calculate initial and final velocity, range, maximum height and time of flight of a projectile: The nature of the vertical acceleration of a projectile. Purpose To analyse the vertical component of the velocity of a projectile in order to determine the nature of its vertical acceleration. Equipment needed Flat board or strong card (at least A4 size), steel ball bearing (as large as possible), stopwatch, sheet of graph paper, sheet of carbon paper. Equipment set-up Clamp Retort stand Ball bearing Ruler Carbon paper 30 cm 30 cm board Graph paper Books for support Theory As a ball rolls across and down an inclined board it will follow a projectile path. Its horizontal velocity will be constant and it will accelerate vertically. Equal horizontal displacements therefore represent equal periods of time. The vertical displacements during these equal periods of time then represent the vertical components of the projectile s velocity. If the projectile is launched horizontally, then its initial vertical velocity is zero. The equations which apply to this motion are: 19 Space

36 Instructions 1. Set up the equipment as shown in the diagram, but do not attach the carbon paper to the board yet. Make sure the board is clamped firmly in place so that it does not move. 2. Roll the steel ball down the ramp onto the inclined board (make the angle no more than 30 o ) and then down the board in a curved path as shown in the diagram. If the ball rolls off the other side of the board, you have rolled it too fast. 3. When you have the roll speed right, tape the carbon paper (carbon side down) on top of the graph paper on the board. As the ball rolls over this its weight will transfer carbon to the graph paper. (If it does not, use a heavier ball.) 4. Roll the ball across the bench and the ramp. 5. Remove the carbon paper and the graph paper from the board. Draw over the ball s carbon path to make sure it is easily seen. 6. Repeat the experiment until everyone in your group has an original copy of the path taken by the ball bearing. Analysis 1. Paste your sheet of graph paper on the next page. 2. Using two major grid squares on the graph paper as a time unit, determine the distance the ball travelled down the incline during each time unit. Put these values in the table. 3. Use these distances to determine the average vertical velocity of the ball for each time interval in cm per time unit. Put these values in the table. Note that because time is not being measured in seconds here, we are unable to calculate absolute values for the acceleration of the ball down the graph paper. However, that is not our purpose as you will see shortly. d 1 t 1 d 2 t 2 d 3 t 3 Time unit t 1 t 2 t 3 t 4 t 5 t 6 Distance ball moved down graph paper (cm) (d 1 to d 6 ) Average velocity of ball down graph paper (cm per time unit) (d 1 t 1 ) etc Space 20

37 Paste your graph sheet with the ball s carbon path here: 21 Space

38 4. Plot the average speed of the ball for each time unit against time (measured in units ) on the axes provided Time unit 5. What does the gradient of the graph represent? What does the shape of your graph tell you? Identify three possible sources of error in this experiment Conclusion Space 22

39 2.13 Outline the contribution to space research of one of: Tsiolkovsky, Oberth, Goddard, Esnault-Pelterie, O Neill or Von Braun. Research report Using a variety of resources, outline the contribution to space research of one of: Tsiolkovsky, Oberth, Goddard, Esnault-Peltiere, O Neill or Von Braun. You may type your answer on a computer and paste the resulting work in here. Note that typical HSC questions in this area could be up to 6 marks in value, so you need to find at least six contributions for the scientist you choose. Provide a detailed account below and then a brief summary of the six points on the next page. Detailed account Space

40 Summary of six points Bibliography Include a bibliography of at least three different types of resources and a brief summary of how you assessed the reliability of these resources Reliability of resources Some sources of information you researched were probably rejected by you, and others were used. Outline how you assessed the reliability of each of the resources you used and why you rejected those you did not use Space 24

41 4.3 Gather and process information to interpret the results of the Michelson-Morley experiment. This is a research task, but you can process your report on a computer and paste it into these pages under the headings given. Theory Because all other known forms of waves required some form of matter to sustain them, scientists in the 1800s assumed that light must also need matter for its propagation. Because light permeated all space, then this matter had to exist everywhere. So they proposed the existence of the aether and spent many years trying to prove that it existed. Their failure to do so was attributed to poor technology and bad experimental design. It was not until Michelson and Morley designed and built their interferometer that progress was made. Part A (a) What was the purpose of the Michelson-Morley experiment? (b) Explain how this purpose relates to the existence of the aether? Space

42 (c) Outline the experiment done by Michelson and Morley in the space below and draw a diagram of their interferometer in the designated space Diagram of interferometer Part B (a) The Michelson-Morley experiment achieved a null result. Explain what this means Space 26

43 (b) What conclusion could Michelson and Morley derive from their experiment?... (c) Research information to determine how scientists in the 1880s interpreted the results of the Michelson- Morley experiment and outline the impact it had on their work and thinking Questions In 1905 Albert Einstein put forward his special theory of relativity. This did not prove nor disprove the existence of the aether, but it did mean that the Michelson-Morley experiment, or any similar experiment, could never get a positive result. Explain why Space

44 4.3.2 In order to improve their chances of finding the aether, scientists of the time predicted several properties it would probably have. List five predicted properties in the table below, and outline the rationale behind each property. Predicted property of the aether Reason for this property Bibliography Space 28

45 4.6 Perform an investigation to distinguish between non-inertial and inertial frames of reference. Purpose To distinguish between non-inertial and inertial frames of reference. Equipment needed Collision trolley, accelerometer, bench pulley, string, mass carrier and masses. Equipment set-up Accelerometer Collision trolley String Bench pulley Masses and mass carrier Theory A non-inertial frame of reference is one that is accelerating. An accelerating bus, or a car braking to stop or turning a corner are examples of non-inertial frames of reference. An inertial frame of reference is one that is at rest or moving with constant velocity. A bus or car moving at constant velocity are inertial frames of reference. Frames of reference which are falling freely under the influence of a gravitational force (i.e. no other forces are acting on them) are also inertial frames of reference. This includes any object in a stable orbit around a planet or star. The Earth is therefore an inertial frame of reference despite the fact that it has a centripetal acceleration towards the Sun. The principle of relativity states that it is not possible to detect whether an inertial fame of reference is at rest or moving without referring to another frame of reference. However, since acceleration involves inertial forces, then any device or experiment which can detect inertial forces can identify a frame of reference that is non-inertial. An accelerometer, a narrow box filled with liquid, is such a device. 29 Space

46 Instructions You will need to take care in this experiment that you stop the collision trolley before it hits the bench pulley. If the accelerometer is knocked off the trolley onto the floor it will probably break. Have one member of your team ready to stop the trolley. 1. Set up the equipment as shown, holding the accelerating mass carrier and masses so that the trolley is stationary. 2. Observe the shape of the surface of the liquid in the accelerometer. 3. Allow the mass carrier and masses to accelerate the trolley as they fall to the floor. 4. Observe the shape of the surface of the liquid in the accelerometer. Observations 1. Shape of liquid in accelerometer when stationary What does this show about the frame of reference of the accelerometer? Shape of liquid in accelerometer when it is accelerating What does this show about the frame of reference of the accelerometer?... Conclusion Questions If you are in a car moving at constant velocity, you can easily see that the car is moving. Does this violate the principle of relativity? Explain your answer Space 30

47 4.6.2 Imagine you are in a rocket ship travelling in deep space. You can see nothing outside the windows. How could you tell whether or not the ship was moving with constant speed, accelerating or stationary? Identify the three different situations which we classify as inertial frames of reference The principle of relativity, in part, states that we cannot do any experiment or make any observation within an inertial frame of reference to determine if we are moving with constant velocity or stationary. However, if we are in a plane, moving with constant velocity, we can tell we are moving by looking at the clouds outside the plane. Are these two statements in contradiction with each other? Explain your answer Space

48 Notes Space 32

49 DOT POINT Appendix 165 Appendix

50 Notes Appendix 166

51 Answers Space The mass on the end of the pendulum, the angle of swing, the stopwatch used to time the swings If your results are correct, you will get about 25 cm (24.8 is the theoretically correct value) Measuring 20 swings splits any human error across the 20 measures and so makes the average time more accurate and the experiment more reliable = 1.63 m s Ensure the string is tied firmly to its point of suspension and that the bob masses are firmly secured. Ensure that the apparatus does not topple over Answers will vary here, but, supposing your answer is 9.6 m s 2, your error is therefore 0.2 out of 9.8 which equates to 2.05%. Your final answer should therefore be expressed as 9.6 m s 2 plus or minus 2.05% Use a regularly shaped mass on the end of the string (the bob) so that its centre of mass can be more accurately found. Use a data logger to measure the period of swing. Interlude exercise I.E.1 Table 1: Results incorporating human and watch error of 0.5 s for each reading. Length of the pendulum (m) Time for 20 swings (s) Period of the pendulum T (s) Period squared T 2 (s 2 ) Calculated value for g using: Average calculated value for g 9.45 Accepting accurate value for g as 9.8 m s 2, calculate the percentage error of this result Plus or minus 3.57% Table 1: Results using stopwatch running accurately. Length of the pendulum (m) Time for 20 swings (s) Period of the pendulum T (s) Period squared T 2 (s 2 ) Calculated value for g using: Average calculated value for g 9.82 Accepting accurate value for g as 9.8 m s 2, calculate the percentage error of this result Plus or minus 0.2% 167 Appendix