STAV – Physics Teachers Conference
Friday 15th February 2013
Sessions C4 & D4
SACs, Apps and Pracs
Paul Fielding (Billanook College)
and
Paul Fitz-Gerald (Ivanhoe Girls’ Grammar School)
"In one of the labs is where they will be. Showing successful SACs and applicable Apps,
Useful demos and also some facts. The Pracs have been proven and their cost is quite
low, Covering all units, who knows where they will go."
iPhone/iPad Apps
Ripple Tank
Cost: Free Lite Version
Cost: $6.49
There is also a free java applet for this app that can be downloaded from:
http://www.falstad.com/ripple/
Quad Sine
Frequency Counter
Cost: $0.99
Cost: $1.99
This app can be used to generate up to four
separate single frequency sounds. It can be used
to qualitatively demonstrate phon curves,
demonstrate beats and resonance in the ear canal.
dB Volume Meter
Cost: $0.99
I have found this app to be no less affective at measuring sound intensity levels than a
commercial device that we bought for use in the lab several years ago.
Student designed extended practical investigation – Assessment Rubric – Unit 3 Physics – SAC 1
Teacher’s comments:
Criterion 1: Plan a practical investigation, using equipment correctly and safely in conducting practical work.
1.
Explains the purpose of the investigation.
2
1
0
2.
Identifies the relevant variables and explains how they were controlled and/or investigated.
2
1
0
3.
Demonstrates the appropriate, safe and accurate use of the apparatus.
2
1
0
4.
Potential risks were identified and strategies to reduce them were included and used.
2
1
0
2
1
0
2
1
0
2
1
0
2
1
0
2
1
0
2
1
0
3
2
1
0
3
2
1
0
1
0
4
3
Criterion 2: Observe and record sufficient data accurately and estimate uncertainties.
5.
Explains how the investigation was undertaken, discusses any problems encountered and their solution.
6.
Evaluates the overall success of the investigation.
7.
Included sufficient data/observations in order to satisfy the purpose of the investigation.
8.
The logbook contained all collected data, observations and comments. It was neatly and logically set out.
4
3
4
3
Criterion 3: Analysis and interpretation of experimental data.
9.
Tables, graphs and diagrams were used to appropriately display data, results and to convey ideas.
4
3
10. Measurements and calculations contained the correct treatment of significant figures.
Criterion 4: Evaluation of the practical work.
11. The student was able to interpret their experimental data and reach relevant and valid conclusions.
5
4
12. Demonstrates an appropriate depth of analysis of uncertainties.
13. An appropriate risk assessment was undertaken and presented in a rubric.
Criterion 5: Knowledge and application of appropriate physics terms, concepts and relationships.
14. Demonstrates an appropriate depth of analysis of the relevant physics.
5
4
3
2
1
0
15. Uses appropriate calculations, physics language and symbols to clearly communicate to the reader.
4
3
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16. Graphs, charts, tables of values and diagrams were appropriately and clearly labelled.
4
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Numerical Summary:
50
Possible Investigation Ideas/Topics
Please remember that in the course of your investigation you need to:
• make sure that you have investigated the effect that two different independent variables have on your
chosen dependent variable.
• use an analysis of your results to predict two outcomes, one by interpolation, the other by
extrapolation, and then experimentally test the accuracy of your predictions.
1. The Simple Pendulum
The Task
Investigate what factors will affect the period, T, of a simple
pendulum.
Independent Variables:
• pendulum length
• mass of bob
• angle of release
2. A Circular Motion Toy
The Task
Investigate what factors will affect the period of rotation, T, of a
circular motion toy.
Independent Variables:
• length of string
• mass of toy
3. The Coefficient Of
Restitution Of A Super Ball
The Task
Investigate what factors will affect the coefficient of restitution, e,
of a super ball.
Independent Variables:
• release height
• temperature of ball
• rebound surface
4. The Coefficient Of
Restitution Of A Basketball
The Task
Investigate what factors will affect the coefficient of restitution, e,
of a basketball.
Independent Variables:
• release height
• ball pressure
• rebound surface
5. The Coefficient Of
Restitution Of A Table
Tennis Ball
The Task
Investigate what factors will affect the coefficient of restitution, e,
of a table tennis ball.
Independent Variables:
• release height
• rebound surface
6. The Coefficient Of
Restitution Of A Tennis
Ball
The Task
Investigate what factors will affect the coefficient of restitution, e,
of a tennis ball.
Independent Variables:
• release height
• rebound surface
• ball type (brand)
• age (usage) of ball
7. The Thrust Generated By
A Propeller
The Task
Investigate what factors will affect the thrust force, F, of propeller.
Independent Variables:
• number of blades
• blade pitch angle
• area of blades
8. The Coefficient Of Static
Friction
The Task
Investigate what factors will affect the coefficient of static friction,
𝜇.
Independent Variables:
• surface type
• area of contact between surfaces
• mass of object
9. The Fall Time Of A
Parachute
The Task
Investigate what factors will affect the fall time of a parachute, t.
Independent Variables:
• area of parachute
• mass supported
• hole size (in top of parachute0
• shape of parachute
Risk Assessments: Yr. 12 Physics Extended Experimental Investigation.
Experiment/Demo/Activity Title:
Location:
Persons exposed to risk: teacher / students
Non-chemical Hazard
Perceived Risk/Injury
Control Measures
•
electrocution
•
safety glasses
•
impact injury
•
heat proof gloves
•
laceration
•
ear muffs
•
skeleto/muscular injury
•
tongs
•
hearing loss
•
dry hands
•
loss of sight
•
face shield
 •
other?
• other?
Other comments:
Waste Management:
 • Sewerage
• Normal rubbish
• Collect for special disposal:
Risk Assessment Matrix:
Probability
Likely
Unlikely
Highly
Unlikely
Fatality
High
High
High
Medium
Major
Injury
High
High
Medium
Medium
Harmful
High
Medium
Medium
Low
1) Assess the
Consequence
2) Assess the
Probability
3) Line the two up to
show the overall
Risk Rating.
Risk Rating
Consequences
Very
Likely
Assess the Risk Rating
for the worst of the
perceived risks above:
OVERALL RISK
RATING:
HIGH
Negligible
Medium
Medium
Low
MEDIUM
Low
LOW
Assessed by:
Signature:
Date:
Resources & References
Simple Pendulum
Drilled ball set of six, 25 mm diameter
Aluminium, brass, copper, lead, steel and wood
Product Code: PH 0109
Cost: $29
http://www.educationmatters.com.au/product-list.php?do=search
Circular Motion Toy
Peter Pan and Tinker bell
Available from: http://www.anime-oz.com/main.html
Cost: $19.95
Super Ball
Just about anywhere!
You do need to be careful though as some of the cheaper ones are not quite spherical in shape and have a
raised mould line around their middle leading to uneven bounces.
For example: A bulk lot of 20 x 27 mm Hi bounce super balls for $15.99 (including postage)
http://www.ebay.com.au/itm/Bulk-Lot-x-20-Rubber-Hi-Bounce-Super-Balls-27mm-New-ToysWholesale-/121063898720?pt=AU_Toys_Hobbies_Wholesale_Toys_Hobbies&hash=item1c2ff87e60
Tennis and Table Tennis Balls
Rebel Sport or any sporting goods store
Basket Ball (& hand pump)
Rebel Sport or any sporting goods store
Propeller Thrust
A bit more expensive this one!
Westlab
Wind Pitch Education Kit
http://www.westlab.com.au/windpitch-education-p-1934.html
Cost: $169.50
Coefficient of Static Friction
Use your imagination on this one – you can use many of the items already in your labs, eg brass weights.
Parachutes
Plastic sheet parachutes could be sourced from:
http://www.dynamicscience.com.au/
or they could be made from recycled materials.
Other materials needed are metal washers and fishing line.
Investigating The Resistance Of Thermistors and LDRs
Part 1A – The Thermistor And Changing Temperature
Aim:
To investigate the effect that a change in
temperature has on the resistance of a
thermistor.
Equipment:
• 1 x thermistor
(Dick Smith Electronics Cat No. R1895)
• multimeter
• connecting Wires
(banana plug & alligator clip at either end)
• hotplate
• blu-tack
• 500 mL Beaker
• Thermometer (-5oC to 110oC)
Your teacher will have already attached the
thermistor to some long connecting wires and
wrapped its exposed metal pins with blu-tack in order
to create a waterproof barrier. Otherwise your
multimeter will be measuring the resistance of the
water not the thermistor!
Using A Multimeter
Caution:
Do not use the multimeter to measure the resistance of a load in a circuit whilst the circuit
is ‘live’. You risk damaging the multimeter if you do. Instead remove the load from the
circuit and measure its resistance using the Ohms (Ω) scale on your multimeter.
Method:
Step 1
Set up your equipment as shown in the diagram above.
Fill the beaker with about 400 mL of chilled water and place the thermometer into the
water and measure its temperature.
Step 2
Place the thermistor into the beaker of water. Do not let it touch the glass walls of the
beaker and make sure that its leads do not touch the hotplate. Wait 5 minutes before you
start taking results. (Why do you need to wait 5 minutes?)
Step 3
Connect the multimeter across the ends of the wires attached to the thermistor.
Step 4
Turn the multimeter to the ohms (Ω) setting and record the thermistor’s resistance and the
starting temperature of the chilled water with the thermometer.
Step 5
Turn the hotplate to high and record the thermistor’s resistance at 10 oC intervals up to and
including the boiling point. You only need to record your answers to the nearest kΩ.
Results:
• Enter your data into an appropriately labelled results table.
• Plot a graph of the Thermistor’s resistance (kΩ) against temperature ( oC).
• Draw in a line of best fit for your data.
Discussion:
Question 1
Does the thermistor behave as an Ohmic conductor? Explain your answer.
Question 2
Use your graph to predict at what temperature the thermistor’s resistance will be 100 kΩ.
Question 3
Use your graph to predict the thermistor’s resistance when the temperature is 45 oC.
Part 1B – The Thermistor And Constant Temperature
Aim:
To investigate the effect that changing the
potential difference across, and the current
flowing through, a thermistor has on its
resistance when at a constant temperature.
Apparatus:
• 2x multimeter, or 1 voltmeter and 1 ammeter
• 1 x 10kΩ resistor
• 1 x thermistor (Dick Smith Electronics Cat No. R1895)
• connecting Wires
Caution:
Do not use the multimeter to measure the resistance of a load in a circuit whilst the circuit
is ‘live’. You risk damaging the multimeter if you do. Instead remove the load from the
circuit and measure its resistance using the Ohms (Ω) scale on your multimeter.
Method:
In the space provided below draw a circuit that shows the thermistor and the 10kΩ
resistor connected in series with a 12V variable power supply. Include in your diagram an
ammeter and voltmeter so that they can be used to measure the current flowing through,
and potential difference across the thermistor. Remember to use a ruler when drawing
your circuit diagram.
Step 1
Measure and record the room’s temperature.
Step 2
Measure and record the resistance of the thermistor as you did in Part 1A.
Step 3
Using the appropriate pieces of equipment set up the circuit you designed so that you can
measure the current flowing through, and the potential difference across the thermistor.
Step 4
Set the variable power supply to 2V and record the current flowing through, and the
potential difference across the thermistor.
Repeat this process for settings on the power supply of 4, 6, 8, 10 and 12V.
Results:
Discussion:
Question 1
Conclusion:
• Enter your data into an appropriately labelled results table.
• Use the data you have collected, and the definition of resistance, to calculate the
thermistor’s resistance for each of the settings on the variable power supply.
Based on your results and calculations, does the resistance of the thermistor change when
it is at a constant temperature but the potential difference across it and current flowing
through it change?
Use a summary of your results to the two parts of this experiment to summarise what you
have learned about thermistors.
Part 2A – The Light Dependent Resistor (LDR) and Changing Light Intensity
Aim:
Equipment:
To investigate the resistance of an LDR as the intensity of
the incident light on it changes.
• 1 x Light Dependent Resistor (LDR)
(Dick Smith Electronics Cat No. Z4801)
• torch or Hodson light box
• 6 x primary red filters from the Hodson light box kits
• blu-tack
• empty 35 mm opaque film canister
• multimeter
• connecting wires
(banana plug & alligator clip at either end)
Your teacher will have already placed the LDR inside the film canister with a hole drilled in the bottom
to let light in for you.
Using A Multimeter
Caution:
Do not use the multimeter to measure the resistance of a load in a circuit whilst the circuit
is ‘live’. You risk damaging the multimeter if you do. Instead remove the load from the
circuit and measure its resistance using the Ohms (Ω) scale on your multimeter.
Method:
Step 1
Set up your equipment as shown in the diagram above. Use blu-tack to hold the film
canister and torch in place.
Connect the multimeter across the ends of the wires of the LDR.
Step 2
Place the torch (Hodson light box) about 20 – 25 cm from the LDR.
Step 3
Turn the torch (Hodson light box) on. Direct the light so that it shines through the hole in
the bottom of the film canister and onto the LDR. Place one of the primary red filters
against the end of the torch. This represents the initial intensity, I o, of your light source.
Step 4
Record the resistance of the LDR for this initial intensity, I o.
Step 5
Place each additional primary red filter in front of the torch and record the LDR’s
resistance. This will give you six data points that you can plot.
Results:
• Enter your data into an appropriately labelled results table.
• Plot a graph of the LDR’s resistance (kΩ) against Intensity, I, (number of filters from 0 to 5).
• Draw in a line of best fit for your data.
Discussion:
Question 1
Does the LDR behave as an ohmic conductor? Explain your answer.
Part 2B – The Light Dependent Resistor (LDR) and Constant Light Intensity
Aim:
Equipment:
To investigate the resistance of an LDR as the intensity of
the incident light on it changes.
• 1 x Light Dependent Resistor (LDR)
(Dick Smith Electronics Cat No. Z4801)
• 1 x 10kΩ resistor • torch or Hodson light box
• 1 x primary red filters from the Hodson light box kits
• blu-tack
• empty 35 mm opaque film canister
• 2x multimeter, or 1 voltmeter and 1 ammeter
• connecting wires
Caution:
Do not use the multimeter to measure the resistance of a load in a circuit whilst the circuit
is ‘live’. You risk damaging the multimeter if you do. Instead remove the load from the
circuit and measure its resistance using the Ohms (Ω) scale on your multimeter.
Method:
In the space provided below draw a circuit that shows the LDR and the 10kΩ resistor
connected in series with a 12V variable power supply. Include in your diagram an
ammeter and voltmeter so that they can be used to measure the current flowing through,
and potential difference across the LDR. Remember to use a ruler when drawing your
circuit diagram.
Step 1
Connect the multimeter across the ends of the wires of the LDR.
Step 2
Place the torch (Hodson light box) about 20 – 25 cm from the LDR.
Step 3
Turn the torch (Hodson light box) on. Direct the light so that it shines through the hole in
the bottom of the film canister and onto the LDR. Place one of the primary red filters
against the end of the torch. This represents the initial intensity, I o, of your light source.
Step 4
Record the resistance of the LDR for this initial intensity, Io.
Step 5
Using the appropriate pieces of equipment set up the circuit you designed so that you can
measure the current flowing through, and the potential difference across the LDR.
Step 4
Set the variable power supply to 2V and record the current flowing through, and the
potential difference across the LDR.
Repeat this process for settings on the power supply of 4, 6, 8, 10 and 12V.
Results:
Discussion:
Question 1
Conclusion:
• Enter your data into an appropriately labelled results table.
• Use the data you have collected, and the definition of resistance, to calculate the LDR’s
resistance for each of the settings on the variable power supply.
Based on your results and calculations, does the resistance of the LDR change when the
intensity of light falling on it is constant but the potential difference across it and current
flowing through it change?
Use a summary of your results to the two parts of this experiment to summarise what you
have learned about LDR’s.
Dick Smith Electronics
Thermistor
http://www.dse.co.nz/dse.filereader?4d40d3f90073fcde2742c0a87f3b071c+EN/catalogs/SUP1000077
Light Dependent Resistor LDR
http://www.dse.co.nz/dse.shop/4d40d3f90073fcde2742c0a87f3b071c/Export/catalogs/SUP1000072