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Copy of Physics Investigation Scaffold

A Scaffold constructed by going through the steps in a Scientific report, focusing on Preliminary Physics for NSW.

Susan Briggs

on 10 January 2013

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Transcript of Copy of Physics Investigation Scaffold

Preliminary Physics Scaffold for Investigations

This is a scaffold for planning and writing investigation reports in the BOS NSW Preliminary and HSC Physics courses. 1. TITLE:
Should Summarise the subject matter of the investigation
"Measuring The Average Speed Of Moving Objects" 2. RELEVANT SYLLABUS DOT POINTS:

Should start with a reference:
MA 1.3.1 Would be: The "Moving About" module, focus 1, column 3, point 1.

Should include the dot points that are supposed to be covered by the investigation
MA 1.3.1: Plan, choose equipment or resources for, and perform a first-hand investigation to measure the average speed of an object or a vehicle. 3. AIM:
Give the purpose of the experiments,
How will it address the problem given in the syllabus dot point/s?
1. To measure the average speed of a moving object (a marble).
2. To show the relationship between speed, distance and time. 4. Variables
Identify the Independent, dependent
and controlled variables.
Remember - In all experiments...
1. Cows - (something CHANGES)
2. Moo - (something gets MEASURED)
3. Softly - (somethings get kept the SAME)
1. I - Independent (The variable YOU change)
2. Don't - Dependent (The variable YOU measure the response in)
3. Care - Controlled (The variables you keep the same to make the investigation fair)
Independent Variable: The distance the marble travels
Dependent Variable: The time of travel
Controlled Variables: The marble used, the angle of inclination of the launch ramp, the launcher team member, the timer team member, the height on the ramp the marble is launched from) 5. Hypothesis
Write a prediction of the trends in the results. Refer to the variables, and how they will relate. Show how your predictions are based on related theory you have learnt.
As the distance the marble is traveling increases, the time taken for the marble to cover that distance at constant speed will also increase. This is given by the conventional physical/mathematical relationship D=TS (also by Δr=Vav x Δt), where distance and time are directly proportional. 6. Equipment:
Clearly list the equipment you will use in
the investigation. Specify its accuracy.
Make sure that if you change/add new
equipment during your experiment
that you also update this list. 7. RISK ASSESSMENT
Identify the hazards and implement precautions to reduce the risk of injuries.
Hazards: dangerous things during the investigation and the reason why its a hazard. ie. Consequences if the dangerous thing leads to harm.
Precaution= Ways to reduce the likelihood of the dangerous thing causing harm, or reducing the severity of injuries caused by the dangerous thing.
Risk Level= The level of risk you take after implementing precautions, can be Low Medium or High. You should add more precautions if the risk is medium or high. 5+7= (cc) image by anemoneprojectors on Flickr 5+7= (cc) image by anemoneprojectors on Flickr E.g. 8. Diagram
Diagrams should be drawn large (more than half the allocated space) using a sharp pencil, eraser and ruler. Labels should use lines NOT arrows, as arrows indicate forces and vectors etc. in diagrams.
You can annotate the diagram and refer to the diagram in your procedure. The point of the diagram is to communicate the setup of your apparatus/ experiment to the reader. 9. Procedure
The point of the procedure is so that the reader can understand HOW you performed the investigation. By reading the procedure someone should be able to repeat your experiment accurately, reliably and validly. The procedure also allows your investigation to be evaluated.

Procedures should be written in short, clear, numbered steps.
Should refer to equipment specifically (for accuracy).
Can refer to the diagram.
Should include steps for reliability (how many replicates/trials)
Each step should start with a verb.
Can include "repeat steps...until..."
Try pretending you are a robot and the procedure is your program whilst you are proof-reading the procedure, in order to make sure the steps are coherent.

Make your first step: "Gather equipment" E.g.
1. Setup the apparatus as shown in the diagram.
2. Make the angle of elevation between the launch ramp and the bench between 10 and 20 degrees and record this angle.
3. Try launching the marble from various points along the ramp until the marbles motion resembles the slowest possible constant velocity along the length of the rulers.
4. Mark this point with a pencil.
5. Place the marble at this point behind the pencil, and lift the pencil when you need to release the marble.
6. Release the marble and use a stop watch to record the length of time it takes for the marble to travel from the starting point where the ramp meets the rulers to the obstacle placed at 0.2 metres away from this point.
7. Replicate step 6 three times for reliable results.
8. Repeat steps 6 and 7 with the obstacle at 0.4m, 0.6m, 0.8m, 1.0m away from the starting point. 10. Results
The results should be presented in a table. The 1st column on the left should be the Independent Variable, the following columns should be the dependent variable trials/replicates/averages. Including this raw data is very important! The last column should usually include averages of the replicates.
Results can also include observations, calculations, diagrams, photographs, any data collected during the investigation, E.g. RESULTS 11. GRAPHS

Graphs are SO important because they tell the story of the variables. A graph shows you:
Which variables relationships exist between
If there is a relationships between variables, what that relationship is.
When there is no relationship between variables.

Your graph drawing and reading skills need to be very well developed by the time you enter your HSC year. E.g. This graph tells us that as the distance the marble travels is increased, the time which the marble takes to travel also increases. Therefore, where speed is constant (given in the investigation by the gradient 1.95m/s), distance is time is directly proportional to distance and vice versa. Rules for Graph drawing:
1. Use a ruler, sharp pencil and eraser.
2. Use more than half the allocated space. The bigger your graph is the more accurate it is.
3. Select a suitable scale for each axis.
4. Plot the points carefully using "x"'s. This is the most accurate way to plot points.
5. Title your graph "(variable on y-axis) as a function of (variable of x-axis)"
6. After plotting all the points, draw a line of best fit.
7. The line should have the same number of points above the line as below the line.
8. The line should have the same horizontal range as the points.
9. The line DOES NOT have to intersect the origin.
10. The graph should have clear axes labels with units in brackets.
11. Calculate the gradient of the line of best fit by substituting its rise over its run.
Never use the gradient point formula with raw data from the table. This gives you a useless figure. (m) (s) (m) (s) CONCLUSION: The conclusion is where you put it all together.
1. Re-read the aims of the investigation and address them in a structured way in the conclusion.

eg. Paragraph 1 - The Conclusion:
1. Objective from the aim: "An objective of the investigation was..."
2. Related trend / pattern / relationship observed in results... "Graph (x) shows that the (independent variable)... (increases/decreases/remains constant) as (dependent variable) (increases/decreases/remains constant)...Therefore the relationship between (independent variable) and (dependent variable) is (directly proportional/inversely proportional/no relationship)."
3. Hypothesis rejected or retained? "Hence the hypothesis "The results show that..." is (rejected/retained). Relate this to the theories/laws related to the subject matter being investigated.
4. Repeat steps 1-3 for all the objectives of the investigation.

Paragraph2 - The Evaluation:
Comment on the accuracy of the results.
Comment on the reliability of the results.
Comment on the validity of the results.
IF your results have an error >5% of a known and valid value that they are supposed to, use this to assess the validity of the results ie. WHEN and ONLY WHEN there is valid known result, eg. Scientific Law, proven mathematical relationship, valid secondary source, etc.
Suggest improvements to the procedure / investigation
Give an overall assessment of the value (validity) of the investigation. Sum up the investigation. E.g.
An objective of the investigation was to measure the speed of an object in motion, a marble. The gradient of the line of best fit on the graph "Distance as a function of time" gives the average speed of the marble as 0.51m/s. The marble motion observed appeared to involve constant velocity during all the replicates. Another objective of the investigation was to show the relationship between speed distance and time. The graphs "Distance as a function of time" and "Time as a function of distance" both give positive linear relationships. This means that Distance is directly proportional to time and vice versa where speed is constant. Therefore the hypothesis is retained.

The results are sufficiently accurate for the aims of this investigation. A metre rule graduated in mm increments was used to measure distances. However, some of the times recorded for the shortest distances (0.2m) were less than the average human reaction time. This means that the measurements taken for time during this replicates were smaller than the human error margin. It does not seem to have diminished the accuracy of the results when viewing the proximity of the relevant points to the lines of best fit in the graphs.
The results are reliable enough for the aims of this investigation as all the lengths tested for the independent variable were replicated 3 times and then averaged before graphing. When viewing the graph you can see that there is very little variation in the results about the line of best fit.
The results of the investigation valid for the second objective of the investigation. The relationship concluded using the graphs is supported by a known physical and mathematical relationship (s=d/t). Sufficient controlled variables were implemented as identified earlier in the report (same marble, same incline, same launch procedure and pilot test for sufficient marble velocity to negate the effects of rolling
friction). The controlled variables ensure that the experiment involves fair testing. Overall the investigation is valid being that the results are reliable, accurate and valid. Also there were sufficient controlled variables to ensure that the investigation was fair.
The investigation's accuracy could be improved in future by using automated methds of releasing the marble and recording its travel time, to reduce human error. Also the reliability of the results could be improved by increasing the number of replicates for each length of the independent variable. Another column on the right could be useful here. 'What to do in an Emergency' or something equivalent. Thoughts?
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